SMTP 554 5.7.1 with smarthost/relayhost

[Jeroen van Meeuwen]

On Wednesday, May 02, 2012 03:26:37 PM Martin Campbell wrote:
> 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
> 

Like René suggested, you should not use a DNS name that itself is a CNAME in 
an MX record.

It is not just violating the relevant RFCs in being "not tidy enough", but is 
actually properly invalid technically.

Kind regards,

Jeroen van Meeuwen

-- 
Systems Architect, Kolab Systems AG

e: vanmeeuwen at kolabsys.com
m: +44 74 2516 3817
w: http://www.kolabsys.com

pgp: 9342 BF08
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