After upgrading from SEP 11 MR2 to MR3, my users 0x800CCC0F Outlook error stopped....for one day, then re-appeared. This issue ONLY occurred during his mail retrieval process.
During my troubleshooting, I had initially opened a command prompt, and issued the command:
telnet pop.myserver.com 110
And received an inline PGP reply, that it was proxying the connection. That prompted me to do a little Googling, but revealed nothing.
I found a MS Kb article that pointed to some troubleshooting steps, but they didn't help at all, and neither did Symantec's kb or forums
Much to my surprise and glee, he started to experiment with his POP settings. After setting his POP connection to SSL, his problems went away!