SMTP 554 5.7.1 with smarthost/relayhost

[Martin Campbell]

On 02/05/2012 14:37, Jeroen van Meeuwen (Kolab Systems) wrote:
> On 2012-05-02 14:35, Martin Campbell wrote:
>> 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"
>>
>> Can anyone suggest a solution to this situation?
> First things first: what is the domain part of the sender email
> address, does it have one or more publicly available IN A and/or MX DNS
> records?
>
> Kind regards,
>
> Jeroen van Meeuwen
>
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

A for placefarm.com is my ISP's URL-forwarding web server