SMTP Messages Stuck in Queue 1

[joelrob]

I upgraded a Windows 2000 server from Exchange Server 5.5 to Exchange Server 2000 three weeks ago. Everything was working fine until yesterday. I have 5 outside domains that all outbound mail to them is being held in the queue. All other outbound mail is being delivered fine. Only these 5 (so far) are getting stuck. 3 of the 5 have definitely received messages since the upgrade. I am receiving the following error in Event ID:

Source: MS ExchangeTransport
Event ID: 4000
Message delivery to the following domain 'CLIENT_DOMAIN.com' failed for the following reason: The connection was dropped by the remote host.

I have checked the databases to make certain we're not blacklisted, we are not an open relay and are not listed as such.

Our e-mail and webhosting are hosted by a third party, but our Exchange server sends all outbound mail directly, it does not go back to them. We have a T1 connection through, and previously had to configure mail to bounce off the ISP's server when we were running 5.5, but I assume this is not the problem as it was working fine until yesterday.

One odd thing is that I've noticed the queue will clear temporarily, all but one of the 5 will show as empty, but then they re-appear.

Any help is greatly appreciated.

 

[robrichardson]

If your using a cisco pix firewall one possible problems could be smtp fixup, switch this off and then watch your queues.

no fixup protocol smtp 25

If your not using a pix forget the above!