Mail.app problems with IMAP and port not allowing access

just set up Mail.app after recovering from disastrous Entourage corrupted database.

i am setting up IMAP for my MediaTemple account.

So, everything went fine, synced folders, accessed accounts using IMAP etc. Folders populated with recent mail still on server.

so, then i quit and restarted Mail.app and now i a getting triangle with exclamation mark' click on it and get the following error:

The server returned the error: The server “accountX incoming” cannot be contacted on port 995.

then i changed to port 143:

The server returned the error: The server “accountX incoming” cannot be contacted on port 143.

so, i am once again (after 2 days of email ****) without email 😟

can someone please help?

thanks