AW: SMTP 554 5.7.1 with smarthost/relayhost

[René Marticke]

> >> I am using Kolab with a smarthost/relayhost because my SMTP server 
> >> has a dynamic IP address. Some SMTP servers block dynamic IP 
> >> addresses.
> >> Occasionally a recipient's SMTP server sends the following error 
> >> message to the smarthost/relayhost SMTP server (which is then 
> >> forwarded back to me).
> >> "SMTP protocol diagnostic: 554 5.7.1 This message has been blocked 
> >> because the return email domain is invalid"

[Rene Marticke] Do you may have to use SMTP-Auth using the relayhost?

> >>
> >> Can anyone suggest a solution to this situation?
> domain part of sender is placefarm.com
> 
> MX for placefarm.com is mail.placefarm.com CNAME for 
> mail.placefarm.com is placefarm.dyndns.org placefarm.dyndns.org is 
> forwarded by my NAT firewall to my Kolab server

[Rene Marticke] <OT>
This violate RFC 821 ans is really dangerous.
A MX must not be a C-NAME. You should use your targetsystem as MX instead of the c-name mapping.
Are you using dyndns because of a dynamic IP? If so what happend if the DNS Update fails and the next one with this IP run a ANY SMTPTrap.
All your mails will be lost and may confidential information are spread to thirdparty.
</OT>

Greetings
René