On the iPhone and iPad (I'm looking at iPhone, but iPad is similar), go to Settings and then Mail, Contacts, Calendars. Tap one of the accounts. Scroll down to where it says Outgoing mail server and has smtp.comcast.net with an arrow next to it. Tap that. On the next page, there should be a primary server and it should be On. Tap On. That should get you to a page that looks like this where you can change the outgoing mail server password.
'If that does not work remove the account
then add it again