I am deleting my long query, as I solved the problem.
The settings that worked for me were:
RECEIVING MESSAGES
imap.comcast.net
Secure to Dedicated Port (TLS)
Port 993
Authentication: Regular
SENDING MESSAGES
smtp.comcast.net
Secure to Regular Port (STARTTLS)
Port 587
Authentication: CHECK Perform SMTP Authentication (RFC 2554)
Select radio button: Same user/password as for Mail Retrieval
Leave UNchecked: Require secure authentication
Leave UNchecked:Use "POP before SMTP" authentication
N.B. I used my full e-mail address, i.e., "" in the User field under Receive Mail. I then tried just entering the username, and that worked, too.
The settings that worked for me were:
RECEIVING MESSAGES
imap.comcast.net
Secure to Dedicated Port (TLS)
Port 993
Authentication: Regular
SENDING MESSAGES
smtp.comcast.net
Secure to Regular Port (STARTTLS)
Port 587
Authentication: CHECK Perform SMTP Authentication (RFC 2554)
Select radio button: Same user/password as for Mail Retrieval
Leave UNchecked: Require secure authentication
Leave UNchecked:Use "POP before SMTP" authentication
N.B. I used my full e-mail address, i.e., "" in the User field under Receive Mail. I then tried just entering the username, and that worked, too.
Edited: - 03 April 2019 08:53:27
(Problem solved)