Notes/Domino 6 and 7 Forum : SMTP Server "strangeness"

We recently upgraded our "hub" smtp server from 5.0.9a to Release 6. Have not seen many problems in bulk, but we have several of internally run applications that send SMTP mail and use this server to route it.

Since the upgrade to Release 6.0.1, two of these applications will routinely either lock up or time out trying to connect and send the mail. From the console.log:

> 04/23/2003 04:00:48.85 PM [0724:0006-0928] SMTP CIServ Listen> Connection Accepted on Port 25 for Session 0CD8000D
04/23/2003 04:00:48.85 PM [0724:0008-07E8] SMTP CITask StateMachine> Sent 106 bytes to 192.168.1.1 (yes, masked for anonymity)

[0724:0008-07E8] S: 220 noteeval.our.org ESMTP Service (Lotus Domino Release 6.0.1) ready at Wed, 23 Apr 2003 16:00:48 -0400<CRLF>
04/23/2003 04:00:48 PM SMTP Server [0724:0008-07E8] State change from Greeting to Greeting
04/23/2003 04:00:48 PM SMTP Server [0724:0008-07E8] Processing in Greeting state
04/23/2003 04:00:48 PM SMTP Server [0724:0008-07E8] State change from Greeting to Connected
04/23/2003 04:00:48 PM SMTP Server: 192.168.1.1 connected
>

...and that is where it stops. Normally, I would expect to see either "HELO" or "EHLO" back from the client side to keep things going, and thus the lockup. Both client and server are listening for something, but nobody's talking.

Connect this client to a 5.0.9a server, and things work just fine.

We've got probably hundreds of SMTP clients connecting on a daily basis, and only two of them seem to fail on a regular basis, and the majority don't ever show any problems.

The only network specific difference on the ND6 server is that we have network compression enabled for TCP/IP, but I would think that is only for NRPC and not SMTP.

Matt? Anyone? Have any ideas about what might be happening here? I've gone as far as disabling all of the ESMTP extensions, but that seems to have no effect either.

Thanks for any help...