I have 2 Cisco UCS environments on the same subnet; call it 10.10.0.x...so a firewall is likely not the problem. The UCS sends out emails using a function called 'CallHome' when there are issues so I've attached each environment to the same SMTP host [an Exchange 2010 server].
My problem is that one UCS sends emails perfectly while the other fails with;
"problem in transporting the message Error in transporting email message for CiscoTAC-1 SMTPclient: sockfd opened...:5 SMTPclient: smtp2.XXXXXXX.com --> 421 4.3.2 Service not available^M SMTPclient: unexpected reply: 421 4.3.2 Service not available^M".
I've verified that the Exchange server lists all the necessary IPs allowed to send email via that server/SMTP host. Both Cisco and my Exchange guys are stumped. HELP!!!
----- Michael W. Oehlert, Network Engineer, GIS