Mac Mail problems receiving messages from Charter.net
I'm running Mac OSX Mountain Lion. I have Mac Mail configured for IMAP connection to charter.net and also to Gmail. Gmail works fine. However, I have problems receiving Charter email.
Get Mail does not retrieve new messages. Neither do I get new email every minute as configured in Preferences (General - Check for new email - Every Minute). However, I do get new email when I take the account offline and then back online.
Mailbox settings are as follows:
IMAP
User Name: name@charter.net
Password: *******
Incoming Server: imap@charter.net
Port: 143
SSL: Off
The fact that I can get email when I go offline/online implies that my mailbox settings are correct. I have no problem retrieving Charter IMAP mail using my iPad or my iPhone. Any other suggestions?
MacBook Pro (15-inch Early 2011), Mac OS X (10.7.3)