I get an error sending mail to Hotmail-based servers from my Exchange 2007 (SBS 2008) server only when SMTP application inspection is enabled on my Cisco 881W router. Mail sent to other domains (eg. Gmail, Yahoo, etc) accept with no problem. Hotmail returns "#500 Unrecognized command ##"
If SMTP application inspection is disabled, mail is delivered immediately to Hotmail with no problems.
Can someone clarify *why* this is an issue. It is my understanding that "inspection" should imply that no modification is taking place.
Thanks for any help, I'm really confused by this..