For those looking for a more direct answer, name resolution for imap.comcast.net seems to be failing recently. Users in the Ubuntu forum thread offer the resolution of changing the account's server to one of the IP addresses reported by "nslookup imap.comcast.net" (use the terminal, Luke.)
Rather than using a fixed IP address, I reset the server name to imap.ge.xfinity.com (the canonical name for imap.comcast.net) then had to submit my password for the newly-named server. Works a treat.
... View more
