Thunderbird: Receive e-mails but cannot send

Receiving e-mails. When I try to send, there is a long pause followed by an error message; Sending message failed. the message could not be sent because the connection to outgoing server (STMP) was lost in the middle of the transaction. Try again

Did you try again?

The connection being lost in the middle of the transaction indicates a problem in routing to me.

Yes. Multiple times. Re-install, reboot, etc. Also, it appears that when I click on “Get Messages” there is no response. The messages just appear when I load Thunderbird or when they arrive.

What are the outgoing settings? They should be on 587, SSL/TLS, normal password, email address for User Name.

Most providers require STARTTLS on 587, but not Spectrum. Select SSL/TLS first, then type in 587 for the port.

The Settings: ![Settings|689x500](upload://p53gYrQwGmfnmaBLBkRHtfm1Jwn.jpeg
Thanks for responding. The problem persists. The following screen clips may contain useful info.
![The Problem|690x461]
Perhaps these will help to describe and clarify the actual problem. The settings were checked with Spectrum. They had no suggestions. The program has been restarted multiple times, The computer has been restarted multiple times.

The images aren’t visible. Try posting them on a service like

Disable antivirus email scanning if it’s enabled.

These are the result of the problem and the settings now set in Thunderbird.
Thanks for your efforts!
Wow, I am wondering if all this is worth the effort.