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    Hi Ludvik,<br>
    <br>
    Thank you  so much for all this information. It is clearer for me
    now.<br>
    <br>
    Olivier<br>
    <br>
    <div class="moz-cite-prefix">On 2017-03-15 00:20, Ludvík Schmarcz
      wrote:<br>
    </div>
    <blockquote
      cite="mid:752E3DCF-E2E4-4504-8FE1-570FE34D041E@blacksun.cz"
      type="cite">
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
      Hi Olivier,
      <div class=""><br class="">
      </div>
      <div class="">question is, if you have one public IP address for
        both servers (behind NAT), or every one have own public IP
        address. In first case do nothing, only correctly set up postfix
        on new server as on old one. In second case you must add second
        server as next mail server (MX record) with low priorinty
        number. Good practice also is to reduce the expiration MX
        records to a small value (600s). In this moment you must turn
        off postfix or block postfix ports by firewall on new
        server, otherwise new server begin receiving mail before
        shutting down the old server. After sync turn off old server,
        turn on postfix (unblock) on new server and delete old MX
        record.</div>
      <div class=""><br class="">
      </div>
      <div class=""><br class="">
      </div>
      <div class="">Ludvik</div>
      <div class=""><br class="">
      </div>
      <div class=""><br class="">
        <div class="">
          <div class="">
            <div style="color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant: normal;
              font-weight: normal; letter-spacing: normal; orphans:
              auto; text-align: start; text-indent: 0px; text-transform:
              none; white-space: normal; widows: auto; word-spacing:
              0px; -webkit-text-stroke-width: 0px;" class="">
              <div style="line-height: normal;" class="">
                <div class="">S pozdravem</div>
                <div class=""><br class="">
                  <div apple-content-edited="true" class=""><span
                      class="Apple-style-span" style="border-collapse:
                      separate; border-spacing: 0px;">
                      <div class="" style="word-wrap: break-word;
                        -webkit-nbsp-mode: space; -webkit-line-break:
                        after-white-space;"><span
                          class="Apple-style-span"
                          style="border-collapse: separate; orphans: 2;
                          widows: 2; border-spacing: 0px;">
                          <div class="" style="word-wrap: break-word;
                            -webkit-nbsp-mode: space;
                            -webkit-line-break: after-white-space;"><span
                              class="Apple-style-span"
                              style="border-collapse: separate;
                              border-spacing: 0px;">
                              <div class="" style="word-wrap:
                                break-word; -webkit-nbsp-mode: space;
                                -webkit-line-break: after-white-space;"><span
                                  class="Apple-style-span"
                                  style="border-collapse: separate;
                                  border-spacing: 0px;">
                                  <div class="" style="word-wrap:
                                    break-word; -webkit-nbsp-mode:
                                    space; -webkit-line-break:
                                    after-white-space;"><span
                                      class="Apple-style-span"
                                      style="border-collapse: separate;
                                      border-spacing: 0px;">
                                      <div class="" style="word-wrap:
                                        break-word; -webkit-nbsp-mode:
                                        space; -webkit-line-break:
                                        after-white-space;"><span
                                          class="Apple-style-span"
                                          style="border-collapse:
                                          separate; border-spacing:
                                          0px;">
                                          <div class=""
                                            style="word-wrap:
                                            break-word;
                                            -webkit-nbsp-mode: space;
                                            -webkit-line-break:
                                            after-white-space;"><span
                                              class="Apple-style-span"
                                              style="border-collapse:
                                              separate; border-spacing:
                                              0px;">
                                              <div class=""
                                                style="word-wrap:
                                                break-word;
                                                -webkit-nbsp-mode:
                                                space;
                                                -webkit-line-break:
                                                after-white-space;">
                                                <div class=""
                                                  style="margin: 0px;">
                                                  <div class=""
                                                    style="margin: 0px;">Ludvík
                                                    Schmarcz</div>
                                                  <div class=""
                                                    style="margin: 0px;">IT
                                                    specialista</div>
                                                  <div class=""
                                                    style="margin: 0px;"><br
                                                      class="">
                                                  </div>
                                                  <div class=""
                                                    style="margin: 0px;">tel.:
                                                    777 726 780</div>
                                                  <br
                                                    class="Apple-interchange-newline"
                                                    style="font-size:
                                                    medium;">
                                                </div>
                                              </div>
                                            </span></div>
                                        </span></div>
                                    </span></div>
                                </span></div>
                            </span></div>
                        </span></div>
                    </span></div>
                </div>
              </div>
              <br class="Apple-interchange-newline" style="line-height:
                normal;">
            </div>
            <span><img moz-do-not-send="true" apple-inline="yes"
                id="DD442B4D-38A3-4659-B668-EE35CD762AA0"
                apple-width="yes" apple-height="yes"
                src="cid:0C09C6EF-C5E3-418B-B7B9-53B51140A406" class=""
                height="150" width="150"></span>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';"><br
                class="Apple-interchange-newline">
              <br class="Apple-interchange-newline">
              <br class="Apple-interchange-newline">
              <br class="Apple-interchange-newline">
              <br class="Apple-interchange-newline">
              <br class="Apple-interchange-newline">
              --</div>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';">--------------------------------------</div>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';">---- Black Sun IT Services
              s.r.o. ----</div>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';">--------------------------------------</div>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';">-- computers - graphics -
              solutions --</div>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';">--- networks - internet -
              intranet ---</div>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';">--------------------------------------</div>
            <div class="" style="font-size: 12px; font-style: normal;
              font-variant: normal; font-weight: normal; letter-spacing:
              normal; text-align: -webkit-auto; text-indent: 0px;
              text-transform: none; white-space: normal; word-spacing:
              0px; -webkit-text-stroke-width: 0px; line-height: normal;
              orphans: 2; widows: 2; margin: 0px; font-family: 'Courier
              New'; color: rgb(41, 81, 169);"><span class=""
                style="color: rgb(0, 0, 0);">------- <a
                  moz-do-not-send="true" href="http://www.blacksun.cz/"
                  class="">http://www.blacksun.cz</a> -------</span></div>
            <div class="" style="color: rgb(0, 0, 0); font-size: 12px;
              font-style: normal; font-variant: normal; font-weight:
              normal; letter-spacing: normal; text-align: -webkit-auto;
              text-indent: 0px; text-transform: none; white-space:
              normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;
              line-height: normal; orphans: 2; widows: 2; margin: 0px;
              font-family: 'Courier New';">--------------------------------------</div>
          </div>
          <br class="">
          <div>
            <blockquote type="cite" class="">
              <div class="">14. 3. 2017 v 22:38, Olivier Boucard <<a
                  moz-do-not-send="true"
                  href="mailto:olivier@pafostech.com" class="">olivier@pafostech.com</a>>:</div>
              <br class="Apple-interchange-newline">
              <div class="">
                <meta content="text/html; charset=utf-8"
                  http-equiv="Content-Type" class="">
                <div bgcolor="#FFFFFF" text="#000000" class=""> Hi
                  Ludvik,<br class="">
                  <br class="">
                  Thanks for the tips.<br class="">
                  I vaguely remember having some mandatory DNS, and
                  reverse-DNS, setup to do before installing. Is it not
                  anymore the case?<br class="">
                  <br class="">
                  Olivier<br class="">
                  <br class="">
                  <div class="moz-cite-prefix">On 2017-03-14 19:21,
                    Ludvík Schmarcz wrote:<br class="">
                  </div>
                  <blockquote
                    cite="mid:F685A7A7-AD06-4217-870D-6C9D3DCC8357@blacksun.cz"
                    type="cite" class="">
                    <meta http-equiv="Content-Type" content="text/html;
                      charset=utf-8" class="">
                    Hi Olivier,
                    <div class=""><br class="">
                    </div>
                    <div class=""><br class="">
                    </div>
                    <div class="">In my experience, the best new
                      installation, add users and use imapsync. If the
                      servers are virtualized, downtime is tens of
                      seconds (only change IP addresses behind the
                      firewall after last syncronisation).</div>
                    <div class=""><br class="">
                    </div>
                    <div class="">Ludvik</div>
                    <div class=""><br class="">
                    </div>
                    <div class=""><br class="">
                      <div class="">
                        <div style="font-family: Helvetica; font-size:
                          12px; font-style: normal;
                          font-variant-ligatures: normal;
                          font-variant-position: normal;
                          font-variant-caps: normal;
                          font-variant-numeric: normal;
                          font-variant-alternates: normal;
                          font-variant-east-asian: normal; font-weight:
                          normal; letter-spacing: normal; orphans: auto;
                          text-align: start; text-indent: 0px;
                          text-transform: none; white-space: normal;
                          widows: auto; word-spacing: 0px;
                          -webkit-text-stroke-width: 0px;" class="">
                          <div style="line-height: normal;" class="">
                            <div class="">S pozdravem</div>
                            <div class=""><br class="">
                              <div apple-content-edited="true" class=""><span
                                  class="Apple-style-span"
                                  style="border-collapse: separate;
                                  border-spacing: 0px;">
                                  <div class="" style="word-wrap:
                                    break-word; -webkit-nbsp-mode:
                                    space; -webkit-line-break:
                                    after-white-space;"><span
                                      class="Apple-style-span"
                                      style="border-collapse: separate;
                                      orphans: 2; widows: 2;
                                      border-spacing: 0px;">
                                      <div class="" style="word-wrap:
                                        break-word; -webkit-nbsp-mode:
                                        space; -webkit-line-break:
                                        after-white-space;"><span
                                          class="Apple-style-span"
                                          style="border-collapse:
                                          separate; border-spacing:
                                          0px;">
                                          <div class=""
                                            style="word-wrap:
                                            break-word;
                                            -webkit-nbsp-mode: space;
                                            -webkit-line-break:
                                            after-white-space;"><span
                                              class="Apple-style-span"
                                              style="border-collapse:
                                              separate; border-spacing:
                                              0px;">
                                              <div class=""
                                                style="word-wrap:
                                                break-word;
                                                -webkit-nbsp-mode:
                                                space;
                                                -webkit-line-break:
                                                after-white-space;"><span
class="Apple-style-span" style="border-collapse: separate;
                                                  border-spacing: 0px;">
                                                  <div class=""
                                                    style="word-wrap:
                                                    break-word;
                                                    -webkit-nbsp-mode:
                                                    space;
                                                    -webkit-line-break:
                                                    after-white-space;"><span
class="Apple-style-span" style="border-collapse: separate;
                                                      border-spacing:
                                                      0px;">
                                                      <div class=""
                                                        style="word-wrap:
                                                        break-word;
                                                        -webkit-nbsp-mode:
                                                        space;
                                                        -webkit-line-break:
after-white-space;"><span class="Apple-style-span"
                                                          style="border-collapse:
                                                          separate;
                                                          border-spacing:
                                                          0px;">
                                                          <div class=""
style="word-wrap: break-word; -webkit-nbsp-mode: space;
                                                          -webkit-line-break:
after-white-space;">
                                                          <div class=""
                                                          style="margin:
                                                          0px;">
                                                          <div class=""
                                                          style="margin:
                                                          0px;">Ludvík
                                                          Schmarcz</div>
                                                          <div class=""
                                                          style="margin:
                                                          0px;">IT
                                                          specialista</div>
                                                          <div class=""
                                                          style="margin:
                                                          0px;"><br
                                                          class="">
                                                          </div>
                                                          <div class=""
                                                          style="margin:
                                                          0px;">tel.:
                                                          777 726 780</div>
                                                          <br
                                                          class="Apple-interchange-newline"
style="font-size: inherit;">
                                                          </div>
                                                          </div>
                                                        </span></div>
                                                    </span></div>
                                                </span></div>
                                            </span></div>
                                        </span></div>
                                    </span></div>
                                </span></div>
                            </div>
                          </div>
                          <br class="Apple-interchange-newline"
                            style="line-height: normal;">
                        </div>
                        <span class=""><span
                            id="cid:0C09C6EF-C5E3-418B-B7B9-53B51140A406"><PastedGraphic-1.tiff></span></span>
                        <div class="" style="font-size: 12px;
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                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';"><br
                            class="Apple-interchange-newline">
                          <br class="Apple-interchange-newline">
                          <br class="Apple-interchange-newline">
                          <br class="Apple-interchange-newline">
                          <br class="Apple-interchange-newline">
                          <br class="Apple-interchange-newline">
                          --</div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant-ligatures:
                          normal; font-variant-position: normal;
                          font-variant-caps: normal;
                          font-variant-numeric: normal;
                          font-variant-alternates: normal;
                          font-variant-east-asian: normal; font-weight:
                          normal; letter-spacing: normal; text-align:
                          -webkit-auto; text-indent: 0px;
                          text-transform: none; white-space: normal;
                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';">--------------------------------------</div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant-ligatures:
                          normal; font-variant-position: normal;
                          font-variant-caps: normal;
                          font-variant-numeric: normal;
                          font-variant-alternates: normal;
                          font-variant-east-asian: normal; font-weight:
                          normal; letter-spacing: normal; text-align:
                          -webkit-auto; text-indent: 0px;
                          text-transform: none; white-space: normal;
                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';">----
                          Black Sun IT Services s.r.o. ----</div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant-ligatures:
                          normal; font-variant-position: normal;
                          font-variant-caps: normal;
                          font-variant-numeric: normal;
                          font-variant-alternates: normal;
                          font-variant-east-asian: normal; font-weight:
                          normal; letter-spacing: normal; text-align:
                          -webkit-auto; text-indent: 0px;
                          text-transform: none; white-space: normal;
                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';">--------------------------------------</div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant-ligatures:
                          normal; font-variant-position: normal;
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                          font-variant-east-asian: normal; font-weight:
                          normal; letter-spacing: normal; text-align:
                          -webkit-auto; text-indent: 0px;
                          text-transform: none; white-space: normal;
                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';">--
                          computers - graphics - solutions --</div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant-ligatures:
                          normal; font-variant-position: normal;
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                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';">---
                          networks - internet - intranet ---</div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant-ligatures:
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                          text-transform: none; white-space: normal;
                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';">--------------------------------------</div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant: normal;
                          font-weight: normal; letter-spacing: normal;
                          text-align: -webkit-auto; text-indent: 0px;
                          text-transform: none; white-space: normal;
                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';
                          color: rgb(41, 81, 169);"><span class=""
                            style="">------- <a moz-do-not-send="true"
                              href="http://www.blacksun.cz/" class="">http://www.blacksun.cz</a> -------</span></div>
                        <div class="" style="font-size: 12px;
                          font-style: normal; font-variant-ligatures:
                          normal; font-variant-position: normal;
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                          font-variant-alternates: normal;
                          font-variant-east-asian: normal; font-weight:
                          normal; letter-spacing: normal; text-align:
                          -webkit-auto; text-indent: 0px;
                          text-transform: none; white-space: normal;
                          word-spacing: 0px; -webkit-text-stroke-width:
                          0px; line-height: normal; orphans: 2; widows:
                          2; margin: 0px; font-family: 'Courier New';">--------------------------------------</div>
                      </div>
                      <br class="">
                      <div class="">
                        <blockquote type="cite" class="">
                          <div class="">14. 3. 2017 v 16:37, Olivier
                            Boucard <<a moz-do-not-send="true"
                              href="mailto:olivier@pafostech.com"
                              class="">olivier@pafostech.com</a>>:</div>
                          <br class="Apple-interchange-newline">
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                            <meta http-equiv="content-type"
                              content="text/html; charset=utf-8"
                              class="">
                            <div bgcolor="#FFFFFF" text="#000000"
                              class="">
                              <p class=""><font class=""
                                  face="Helvetica, Arial, sans-serif">Hi,</font></p>
                              <p class=""><font class=""
                                  face="Helvetica, Arial, sans-serif">I
                                  have an old Kolab 3.3 running on an
                                  old CentOS 6. I would like to migrate
                                  to a new server running CentOS 7 with
                                  the latest Kolab.</font></p>
                              <p class=""><font class=""
                                  face="Helvetica, Arial, sans-serif">What
                                  would be the steps (not in details
                                  just the overall process) to do such a
                                  migration with no service interruption
                                  (keeping the old server running)?<br
                                    class="">
                                  Especially concerning the DNS
                                  configuration.</font></p>
                              <p class=""><font class=""
                                  face="Helvetica, Arial, sans-serif">Thanks</font></p>
                              <p class=""><font class=""
                                  face="Helvetica, Arial, sans-serif">Olivier
                                  Boucard<br class="">
                                </font></p>
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