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550 Recipient address not accepted [message #1479] Mon, 03 July 2006 13:22
richardhall
Messages: 2
Registered: July 2006
Junior Member
Is it possible for NoSpamToday to output a '550 Recipient address not accepted' message via SMTP? Does NoSpamToday filter on recipient email addresses?

It looks like external mailservers are opening smtp connections to our mailserver, saying HELO, and then querying if the sender's mail account exists, presumably to determine the email was not sent with a spoofed or makebelieve email address.

At present the above message seems to be generated in the response from our mailserver. At first we thought it might be our mailserver software itself but after checking with the developers responsible for it, that software is only capable of returning messages like '503 5.5.1 Need MAIL before RCPT' where there is always an additional protocol message definition code (5.5.1) alongside the SMTP response code (503).

We're running in an environment whereby we have multiple domains all aliased to accounts on one mailserver. I don't know if that makes any difference.

Any suggestions welcome.

Regards,

Richard Hall LRSM BSc MBCS
Software Developer
Source Software Ltd

Re: 550 Recipient address not accepted [message #1480 is a reply to message #1479] Tue, 04 July 2006 14:09 Go to previous message
support
Messages: 919
Registered: April 2004
Senior Member
> Is it possible for NoSpamToday to output a '550 Recipient
> address not accepted' message via SMTP? Does NoSpamToday filter
> on recipient email addresses?

NoSpamToday! will issue a 550 "Recipient address not accepted" message
if the sending MTA (mail transfer agent) tries to send mail to a recipient address
not specified in the Open Relay Protection list. If this list is left empty, your mail
server should have relay protection enabled and issue a 550 message itself in this case
(remember that NoSpamToday! is a transparent SMTP proxy and thus accepts
a recipient address only if your mail server also accepts it).

> It looks like external mailservers are opening smtp connections
> to our mailserver, saying HELO, and then querying if the
> sender's mail account exists, presumably to determine the email
> was not sent with a spoofed or makebelieve email address.
>
> At present the above message seems to be generated in the
> response from our mailserver. At first we thought it might be
> our mailserver software itself but after checking with the
> developers responsible for it, that software is only capable of
> returning messages like '503 5.5.1 Need MAIL before RCPT' where
> there is always an additional protocol message definition code
> (5.5.1) alongside the SMTP response code (503).
>
> We're running in an environment whereby we have multiple
> domains all aliased to accounts on one mailserver. I don't know
> if that makes any difference.

No, that does not make a difference. One NoSpamToday! instance can handle multiple mail domains.



Customer Support
Byteplant GmbH
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