The first and the second entry is ok but in the third one there something weird.
Although “250 receipent ok” SMTP code the message was not transferred. In the 4th one and others (I croped) messages to domain XXX.com is not delivered with error 400.
14.09.2005 08:53:58 Router: Transferred 1 messages to XXX.COM (host postman2.XXX.COM) via SMTP
That would be SMTPClientDebug actually if you want to see what is happening to outbound mail.
This looks like a timing/timout problem. Something is disrupting TCP connectivity during the SMTP conversation anyway. Could be a broken firewall.
You might also look at MTU size - that could cause these symptoms if it is too big and MTU path discovery is being sabotaged by an overzealous firewall (asx is very often the case). Read this page towards the bottom for a howto:
Yes this could be… there is linux box as a firewall(Red Hat 6.2) using IP Chains.I have problems with sending large (<100KB) mails. They stuck at mail.box. And when I bypass firewall they immediately be sent.
I’m having same issue when certain mail servers connect but don’t deliver their messages. Only started since upgrading to version 7. Only 2 external mail servers being affected so far!