No IMAP, sorry. Comcast does not provide an IMAP interface to the mail servers. Many have requested it, but those requests have been ignored for public use so far.
As for SSL, I would recommend it, espcially if you use unencrypted WiFi networks or do email off the Comcast netwrok, such as while travelling on vacation, etc. SSL ensures your email messages can't be sniffed in transit between you and the mail server.
For incoming, use port 995 with SSL, for outgoing, use port 587 with SSL (in Mac Mail) and make sure you do have outgoing password authentication active (it's required on port 587). Just follow the EXACT instructions in the link you posted.