telnet to exchange server displays error message 220 *****

When telneting to an exchange server you get the following errorr:
220 *******************
When you run EHLO you get the following error
500 5.3.3 Unrecognized command

This can happen when a cisco device is using
"fixup protocol smtp 25"
or
"inspect esmtp"

Also AV's have been known to cause these issues.

See this page for more detail:
http://www.binarywar.com/2009/11/cisco-pixasa-causes-smtp-banner-corruption/