Please provide screenshots of the errors you are getting Is this an IMAP or POP account? Are you running Thunderbird on a computer, Mobile, Tablet or something else (please specify)? Which Operating System are you using?

I am having the same issue: my legacy Spectrum email accounts can receive emails (IMAP and POP), but can't send (SMTP). I used their chat and called them, and they said that it would be the same server (mail.twc.com or mail.brighthouse.com) for both IMAP/POP and SMTP. I've even double-checked the ports.

I keep getting connection time-out errors (even though they seem to be awfully instantaneous for "time-out" errors - like, 1 second, if that!).

I'm wondering if it has anything to do with installing Thunderbird directly from the Windows 11 app store, instead of downloading directly from mozilla.org.

Anyway, this used to work on my wife's old laptop (before it got hacked by Russians) which was running Windows 10. This new laptop, though, I cannot get it to send via SMTP server. (I end up using Spectrum's online webmail to send emails, but that's gonna fill up fast, since I need to send large attachments for my wife's architecture work account.)

I have been unable to find assistance re - Over recent weeks I have been unable to send emails from my gmail account on Thunderbird with the message:- Sending message failed. The message Could not be sent because connection to Outgoing Server (SMTP) failed. The server may be unavailable or or is refusing SMTP connections. Please verify that your Outgoing server (SMTP) settings are correct and try again.

Have had the same problem for months: can't send email. Various error messages. Have tried all sorts of options in settings, but no luck. I'm about to delete Thunderbird. Have used it since it was called Eudora, but now it's useless.

I've had the exact same problem since the last release of Thunderbird about one month ago (version 138). I downgraded to the Thunderbrid "extended support release" (128.10esr), and it solved my issue right away.

To make sure it was a version problem (and not me who entered incorrect information at some point when configuring my account on Thunderbird), I tested upgrading again to the most recent "standard" version (138), and BAM, the problem reappeared.

So in my case, the problem definitely comes from Thunderbird's last update, not from the server. (FYI, I use IMAP for receiving, and SMTP for sending, more info below). The solution here for me is to downgrade to Thunderbird ESR 128.10 until this bug is fixed by Thunderbird developers.

Therefore, if you have the problem of "can receive, can't send", you should try downgrading to the "ESR" version of Thunderbird to see if it solves your problem too. To download this version, on the Thunderbird download page (https://www.thunderbird.net/en-US/download/), choose "Thunderbrid extended support release" in the Release Channel dropdown list.

I hope it will help some people, as I lost a lot of time with this problem.

In case a Thunderbird developer reads this, here is the detailed configuration of the email server I use (I won't report a bug on bugzilla, as the reporting process is too complicated and I just don't have the time for that):

INCOMING SERVER: IMAPS imap.<redacted>.fr Port 993 Connection security : SSL/TLS Authentication method : Normal

OUTGOING SERVER: SMTP smtp.<redacted>.fr Port 587 Connection security  : STARTTLS Authentication method : Normal

Also, the email system is hosted on a Microsoft Exchange On-Premise server (not my choice, but it is what it is).

I have the same problem has anyone got the solutions yet?