Thunderbird cannot connect to smtp server, but gets incoming via pop3

Yesterday Thunderbird started failing to connect to my smtp server.  It does connect to the pop3 server and get emails.  I turned on smtp logging in Thunderbird and only see a message stating it is attempting to connect to smtp server.  No error messages.  No changes were made to Thunderbird.

I assume either NIS or Windows is blocking access.  I checked the settings for Program Control and Thunderbird is listed.  Only thing I remember is Windows Update installing something a couple of days ago when I shut down.  Does anyone have any ideas on what to look for?

BTW, I attempted to turn off scanning of outgoing messages in NIS but still got the same result.  Also, disconnected router from ISP and reconnected.  

 

Leroy

I tried to ping the smtp server from a command line.  It was unsuccessful, did not seem to resolve the DNS.  I pinged smtp servername from a different computer on a different network.  It pinged successfully.  I will try the IP address when I get home.

 

Any ideas on why DNS would resolve the pop3 servername but not the smtp server?

 

Leroy

Came home after work, rebooted laptop, Thunderbird now can send emails.  I don't know what was going on.  I made no changes.

 

The ping to the smtp server that was not working before works now.  Something was crosswise somewhere.  Probably not on my system.

 

Leroy