Thunderbird update breaking outbound email through CenturyLink
As of today, I'm unable to use Thunderbird to send outbound mail though my ISP - CenturyLink.net.
After much frustration, testing, and talking with CenturyLink personnel, I noticed that Thunderbird had updated itself today to version 91.5.1. Since I'm able to send mail through the CenturyLink mail server - smtp.centurylink.net - via Android and their webmail, this update seems suspect.
Further, after logging on to an old computer I no longer use with an old version of Thunderbird (78.x.x) I was also able to send email successfully.
So, it appears evident that the 91.5.1 update has broken Thunderbirds communication to the CenturyLink outbound mail server.
I'm running Windows 10, using port 587, normal password authentication and STARTTLS security.
I'm about to uninstall Thunderbird and go back to an earlier version, but I thought I'd first submit this issue.
Thanks in advance.
Chosen solution
How about just using ssl/TLS are recommended by your mail provider.(TLS if available is what they say) STARTTLS has been the subject of fixes because it was identified as a security risk. The changes apparently do break on some servers, especially those that have it, but it is not a published recommendation of the provider.
A test of the servers SSL/TLS returns a fail, but it does support the necessary protocols for Thunderbird to connect using SSL/TLS. with the requisite 2048bit key length https://www.immuniweb.com/ssl/smtp.centurylink.net/L1FdPbBY/
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Try deleting and reconfiguring your SMTP server and then confirm it is set to that account by checking tools>account settings and click the account name and view in right side pane that it is set properly.
Thank you, but verifying that I'm using the correct SMTP server and parameters doesn't help. I've also tried - as you suggested - deleting the account and building a new one configured with the correct SMTP server and parameters, that too, didn't work.
To me, the key is that I can send mail through the CenturyLink server with an Android tablet, through the CenturyLink webmail, and, using a Windows 10 PC with an older version of Thunderbird. The only send failure occurs with Thunderbird 91.5.1. All of these platforms successfully receive mail.
I've also tried both the STARTLS and SSL/TLS options for the outbound server, to no avail.
At this point, if I don't see the likelihood of a Thunderbird update being released, I'm dropping back to an old version from early January or December 2020, and disabling updates.
Best regards...
Chosen Solution
How about just using ssl/TLS are recommended by your mail provider.(TLS if available is what they say) STARTTLS has been the subject of fixes because it was identified as a security risk. The changes apparently do break on some servers, especially those that have it, but it is not a published recommendation of the provider.
A test of the servers SSL/TLS returns a fail, but it does support the necessary protocols for Thunderbird to connect using SSL/TLS. with the requisite 2048bit key length https://www.immuniweb.com/ssl/smtp.centurylink.net/L1FdPbBY/