My wife can no longer send email using Outlook and smtp.comcast.net as her
outbound email server.  She's been using this for years.  I'm running
Thunderbird under Linux, and I lost my ability to send email, although we
had no problem with receiving email.  I called Comcast and they said to
change the port from 25 to 587.  I did this with Thunderbird, and it
worked.  However, changing the port under Outlook did not resolve the
problem, and my wife still cannot send email.  She called Comcast and they
told here that the problem was with Microsoft!  I seriously doubt it.
Anyway, any suggestions would be greatly appreciated.

As a workaround, I may install Thunderbird for Windows and see if that
works...