Split from this thread.

I am also having problems sending because some messages, which are not in my outbox are blocking most others from sending. I am on Win 10, but I also had it on Win 8.1

The message could not be sent. The setting for your outgoing email [SMTP] server might need to be configured. To find the server settings for *** Email address is removed for privacy ***', please contact your email service provider.

Subject 'Re: New Ride to Benderson Lake and back.'
Server Error: 550
Server Response: 550 5.1.1 <*** Email address is removed for privacy ***> recipient invalid domain
Server: 'smtp.comcast.net'
Windows Live Mail Error ID: 0x800CCC79
Protocol: SMTP
Port: 587
Secure(SSL): No

the email address is incorrect and came from another email which I replied all to. Should be columbus.rr.com