Exchange 2003-2007 mail stuck in queue between servers

Had a situation where we were migrating from 2003 to 2007 and were unable to send mail between hosts, here are the things we tried and ultimately the solution


  1. Cannot send mail between servers
  2. On 2003 mail stuck in queue – Unable to bind to the destination server in DNS
  3. On 2007 mail stuck in queue – unable to authenticate with remote server

Actions taken

  1. Checked the SMTP virtual server on 2003 for smart host and external DNS – removed the external DNS
  2. Deleted and re-created routing group connector
  3. Removed 3rd party mail filter software
  4. Verified AD replication
  5. Validated DNS records
  6. Disabled Firewalls
  7. Enabled verbose SMTP logging – this is where we were seeing that 2007 was doing a ehlo then a quit

Solution:  Found that SMTP on the 2003 was missing  the X verbs (x-EXPS, X-Link2state, xexch50,) this causes the 2007 to not see the 2003 as an exchange server and quits, the solution was to re-install exchange on the 2003 server to re-enable the verbs in SMTP


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