Exchange Sender Verify Erros


I'd be very grateful if any of you could help with this maddening problem.

Our Exchange server in general recieves and sends mail with no problem.

However a few (and possibly increasing) number of domains are generating sender verify errors.

The Exchange server is 2003 Build 7638.2 SP2.

the domain is with an mx record of

Reverse DNS is set up and the IP matches the MX(A) record as far as i can tell.

The Anti - Spam we use is Pure Message 3.0.2.

A coupld of event log entries are listed here, and all email addresses listed are present and correct.

We do not appear to be on any blacklists - nor do we appear to be an open relay
SMTP Logging is set to maximum.

This is an SMTP protocol error log for virtual server ID 1, connection #109. The remote host "", responded to the SMTP command "rcpt" with "550-Verification failed for <>  550-The mail server could not deliver mail to  The account or domain may not exist, they may be blacklisted, or missing the proper dns entries.  550 Sender verify failed  ". The full command sent was "RCPT TO:<>

This is an SMTP protocol error log for virtual server ID 1, connection #16. The remote host "", responded to the SMTP command "mail" with "550 Unable to verify sender  ". The full command sent was "MAIL FROM:<> SIZE=9118  ".  This will probably cause the connection to fail.

Any thoughts?

Many thanks in advance.
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This could be a problem with the SPF record.  Check that there is an SPF record and that it lists all authorised servers
MullsterAuthor Commented:
I'd though of that, however the current domain host's DNS does not support SPF so I can't make the amendment. I have applied for a domain transfer, and once done I'll be trying that.

Thanks for the suggestion and I'll update once the transfer is done.

Any other suggestions in the meantime would be welcome.

THE SPF record is of type TXT.  If can add a TXT record you should be able to add an SPF record
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MullsterAuthor Commented:
I submitted the records to them to be added but was informed that they couldn't. Its a hands off relationship so I don't have direct access to the DNS.

This was their response:
Unfortunately, our name servers do not currently support SPF records. I will continue investigating why mail servers are unable to look up the domain.

Another reason for moving the hosting so I'll continue down that route in order to get some control over it.

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MullsterAuthor Commented:
Having moved the domain and added the SPF all seems to be well. Points are yours.
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