Outgoing mail error, can't resolve

I have an error when I try to send outgoing mail.    The error occurs when I uses Thunderbird on my Windows laptop and on my Ipad.  It does not occur on my Android phone.  

I have checked the server settings and port a dozen times over the last 4 days.  Cannot resolve the issue.

Anny suggestions are appreciated 

This is the full error message:

Sending of the message failed.
An error occurred while sending mail: Outgoing server (SMTP) error. The server responded:  resomta-c2p-555482.sys.comcast.net resomta-c2p-555482.sys.comcast.net Excessive failed authentication, ESMTP server temporarily not available.