Exchange SMTP Connector issues over Cisco firewall
Recently I had a run in with setting up a TLS encrypted SMTP connector on an Exchange 2003 server. The problem ended up being with the Cisco ASA/PIX firewall device dropping the TLS encrypted SMTP packets. If you notice that your SMTP connector works fine without TLS encryption but fails with the encryption turned on then you are experiencing the ESMTP inspection feature on your Cisco ASA/PIX firewall. The fix is to turn off the protocol as follows.
In order to allow the e-mails with TLS enabled, disable the ESMTP inspection feature as this output shows:
pix(config)#policy-map global_policy
pix(config-pmap)#class inspection_default
pix(config-pmap-c)#no inspect esmtp
pix(config-pmap-c)#exit
pix(config-pmap)#exit
Instruction verified by Cisco…
Disable ESMTP inspection