550 5.7.1 Unable to relay for error

I'm getting this error on an sbs 2003 with exchange 2003, all latest SP's.
550 5.7.1 Unable to relay for xxx@xxx.com
Users are receiving this error when sending to SOME domain, not all.
There was an open relay on this server which I fixed.
The exchange settings are correct: relay > relay for only the list below > local ip of the server.
The domain is not blacklisted anymore.
Any idea why some users are getting this msg?
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MikkkConnect With a Mentor Commented:
It's ok.
It seems that is an incomming attempt to send a mail from outside. is trying to use your exchange as a relay host, as it probably did some days ago, and now it is unable to send any mail.
This event is a good news, because says that you are not an open relay.

You can make some test:
Connect to your SMTP mail from ouside the internet with a telnet:

telnet 25
helo anything
mail from: some@mail.com
rcpt to: someother@externalmail.com
<- here will give you an error saying you can't send mail from outside to outside.

suppsawsAuthor Commented:
Another strange thing is the eventlog.
I put smtp logging to the max and I am getting these errors:

Event Type:      Error
Event Source:      MSExchangeTransport
Event Category:      SMTP Protocol
Event ID:      7010
Date:            16/10/2007
Time:            13:10:52
User:            N/A
Computer:      SBS
This is an SMTP protocol log for virtual server ID 1, connection #349. The client at "" sent a "rcpt" command, and the SMTP server responded with "550 5.7.1 Unable to relay for dawson@thecsgroup.com  ". The full command sent was "rcpt TO: <dawson@thecsgroup.com>".  This will probably cause the connection to fail.

I wonder why I am still seeing these errors because I cleaned the whole queue folder .... ??
As you say, this is the normal behaibor of an open relay domain.
If you cleaned all databases (spamcop, spamhaus, ...) you have to be patient and wait some weeks in order to all servers (like to be update with the new database.

Some servers update themselves only once a week or once a month, so it is possible that some ones allows you to send mails and others not.
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suppsawsAuthor Commented:
The domain isn't blacklisted on any of the blacklists, so I don't think this is a blacklist problem.
The strange thing is the MANY events in the eventlog.
Even though I fixed everything the eventlog is filling with thousands of errors  with 550 5.7.1 Unable to relay for xxx@xxx.com
How come these errors are generated? This looks like some kind of script that is trying to send the emails??
The event log is filling in every exchange attempt to send the mail to the outside server, and that outside server returns that error. I think it is a normal thing.
When did you remove your domain IP from the blacklists? some weeks ago? this week?
I still think that the problem is that your IP WAS blacklisted and the removal of the servers is still not replicated to all mail servers of all over the world. This is very common when you remove from the blacklist some ip.
I think is is a problem that has to be resolved with time. In 2 or 3 weeks it has to be accepted in all mail servers.
suppsawsAuthor Commented:
I don't think it's an outside server that is generating these events, because I see them in my local eventvwr.
It's like some kind of script that is trying to relay via our smtp server but it can't because there is nog relaying allowed.... .
The ip was on only one blacklist, and when I check it there it's removed, so I don't think this is a blacklist issue.
suppsawsAuthor Commented:
Yes, you are right!
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