I can no longer send email from iPad2 using Comcast. Email goes to Outbox with error msg, "the server address (my Comcast.net address) was rejected by the server". I can receive Comcast email on iPad. I can send via Comcast emails from my PC.
Make sure that your email accounts match; meaning they have to be the same format. Either IMAP or POP. If one device is setup as IMAP and the other is set up as POP they won't work.