Outgoing mail server gone under El Capitan
Immediately after installing El Capitan, I am unable to send emails. However, I'm still receiving them. Note the following oddity ... although I once had an email address "drastal@comcast.net" it has been inactive for years. Nonetheless, it appears when I view the "Internet Accounts" tab under "System Preferences". I've asked staff at the Apple Store to resolve this twice before, and no one seems to understand why it's shown there. Yet my drastal@icloud.com account has worked perfectly, until I installed El Cap.
The contents of my Mail Preferences are shown below. Thanks in advance ...
iMac (27-inch Mid 2010), OS X El Capitan (10.11)