Error when SMTP Callout enabled

[Nidhoggr]

Anytime I enable the SMTP Callout I cannot receive any E-mail on that domain. I get a bounce, PERM_FAILURE: SMTP Error (state 9): 550 (result of an earlier callout reused). Now I have it disabled however I now have over 60,000 in the incoming and an average of 8000 in the filter. Now I know that most of these messages are for dead addresses with the outgoing with over 35,000 of useless crap and used spam filtering. Some of the messages in the filter are over 7h old. I need some way of getting that number down.
I have a Sempron 3000 with 1.5 GB of ram the mail cleaner is fully updated. Any suggestions would be very helpful. My decrepit e-mail server cant get a LDAP anything working so I need something. The sad thing is we only host 350 users

[Nidhoggr]

I think I found out why the SMTP Callout isnt working. the Mail server doesnt seem to accept from a Null sender. is this how SMTP Callout works?

[Nidhoggr]

well silly me I fixed the problem. we were useing an old E-mail server that had null sender dissabled then it got patched so that I lost the interface to change it. after digging through the registry and changeing that back SMTP Call out works fine now... thanks for letting me vent to find the problem

[the_fbi]

Good news its working.

May be worthwhile putting the details of your mailserver, ie. software/version and the fix (registry changes) you applied, in case other people have the same issue.