My mail server flagged spam!

Matthew Seaman m.seaman at
Thu Oct 21 05:42:23 UTC 2010

On 21/10/2010 01:10, Marwan Sultan wrote:
>   if I check that domain in
>   it complains "Warning - Reverse DNS does not match SMTP Banner"
>   could it be the SMTP banner flagging the mail as spam?

This is certainly possible.  It would add spam points on my servers.

The address in question is the one presented by your mail server during
the SMTP dialogue -- the first line it sends in fact.  Something like this:


By default it will use the hostname of your server, but you can override

It is this address that you have to be really strict about: the address
should resolve to the IP that the server connects via (not necessarily
the IP of the server if there are NAT gateways involved), and a reverse
lookup of that IP should return the name again.

This name used in the EHLO banner doesn't have to be anything to do with
the addresses on the e-mail, except in as far as either side is using
SPF and you have chosen to add that information to the SPF selector(s).
 SPF seems to be going out of favour now, and sensible mail admins
didn't make accept/deny decisions entirely on pass/fail of SPF tests,
but still, for best results with a mail system, you should take care to
get that right.



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP:     Ramsgate
JID: matthew at               Kent, CT11 9PW

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