KDE over Fedora 43. Here is a telnet test, which eliminates any client issues. However, the same timeout occurs with Thunderbird.
However, I can ping the server.
Here’s the result from Thunderbird:
I tried using a proxy to get out of ATT’s space. Same result. smtp.mail.com also produces the same result. Obviously, this is mission-critical. At times (when I have the blessings of the email gods) it works. However, most of the time, I get a timeout.
smtp uses port 25 originally and 587 more commonly these days.
telnet defaults to 23.
Have you tried specifying a port for your telnet command?
P.S Don’t post pictures of straight text - pictures can’t be searched for, whereas text is trivial to index.
also, netcat (nc) is considerably more potent than telnet and is installed by default.
Thank you very much. I’ve been at this since RH 7.x and have too much rattling around in my brain. It’s been 20 years since I used telnet to test Postfix. 587 works, which means that the problem resides with my mail client, Thunderbird. Now I can figure out what the problem is.
Been there, done that. You’re not alone! 
The thunderbird smtp setting for gmail is usually something like
Description: Google Mail
Server Type: SMTP Outgoing Server
Server Name: smtp.gmail.com
Port: 465
User Name: xxxxxxxxxxxxxx@gmail.com
Authentication method: OAuth2
Connection Security: SSL/TLS
Have you enabled outgoing mail in Gmail?