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Using Thunderbird 115.18.0esr Supernova 64-bit on Mac laptop OS 10.13.6. Worked fine for years, with ongoing Thunderbird updates, even though Mac OS is 32-bit. Suddenly, after 10/6/26 can't retrieve emails although I can see them on the ATT Yahoo server website. Can still send emails with Thunderbird. Inbound server settings are: POP server inbound.att.net, Port 995, SSL/TLS, Normal Password (I long ago created a Secure Mail Key, and even tried creating a new one). But inbound server name doesn't show in Saved Passwords (only outbound server with Secure Mail Key as password)? I have tried everything suggested, repaired my inbox folder, updated Thunderbird files, etc. in Profile as recommended. But still no prompt for password when attempting to get messages. Just shows "Done" at bottom left with no new messages received. But new messages are seen on server website. So it appears that Thunderbird isn't able to connect to the ATT Yahoo server to get emails. Why? And what else can I do? I love Thunderbird and want to continue using it.

ever since last update... can't send emails

Send Message Error Sending of the message failed. An error occurred while sending mail. The mail server responded: E5rTxqhwZYbiPE5rUxBTZm DMARC Policy Enforcement: https://postmaster.comcast.net/smtp-error-codes.php#ODM00001. Please check the message and try again.

Not sure what is going on but all of the sudden my inbound server is not allowing emails in. Outbound works. AT&T says its a Thunderbird issue. My computer guy cannot figure it out. Help. I can only receive email on AT&T

My eMail has worked fine for many years - until this morning.

 When I first tried to "get messages", I got a response, "connection to inbound.att.net server reset".
 I restarted Thunderbird, and then the computer (Windows 11), and when I tried again, I got, ""inbound.att.net (POP) .. certificate revoked".
 I can login to my ATT webmail, but I can't download eMail to my computer via Thunderbird.

... In my attempt to upload this question, I looked for the TB Version, but it said to update Thunderbird. I did so, not it is back to telling me "connection...reset"

 Please help!

when trying to download email today, says certificate for inbound.att.net is not trusted. android email and browser email are OK.

My inbox is not updating for my personal or work account. I recently reset the password for my company account and since then I have not received new emails on thunderbird.

I recently set up Thunderbird for Windows as a troubleshooting step for my Yahoo Mail account which has been generating an incessant number of authentication pop-ups in Microsoft Outlook (Classic) for Windows. I had been using New Outlook for many months before switching to Classic Outlook a couple of weeks ago. With New Outlook, there had been no authentication issues nor pop-ups appearing. I have been using the OAuth authentication, not app passwords, in all cases.

Setup within Thunderbird was relatively easy and the OAuth authentication went through without issues. The account has synchronized and seems to be continuing to do so as I read, delete, and send messages.

However, when I went in to the Activity Manager, I'm seeing a number of errors, appearing every 10-15 minutes or so. They read as follows:

• Alert from account xxx@yahoo.com: AUTHENTICATE Server error - Please try again later

• The current operation on 'Inbox' did not succeed. The mail server for account xxx@yahoo.com responded: UID FETCH completed.

• The current operation on 'Inbox' did not succeed. The mail server for account xxx@yahoo.com responded: p.

Can anyone help me understand what they mean? It would help me stabilize Thunderbird and might give some clues as to what is happening in Outlook Classic for me. It would seem some have authentication issues with Yahoo on different platforms while the service works perfectly fine for others. I would like to move away from Yahoo as I find it finicky with a number of its features, but I'm a long-term user (25+ years) and don't see that being a practical solution at the moment.

Thanks!

I am assisting an elderly user with a personal @hotmail.com account that receives email successfully in Thunderbird but cannot send. I have confirmed they can send and receive emails from their online outlook.com portal. The user's computer setup is as follows:

• Windows 11 (with latest updates).
• Thunderbird 153.0.2 (64-bit).
• A personal @hotmail.com account with the following server configurations:

  -> Incoming IMAP: outlook.office365.com, port 993, SSL/TLS, OAuth2, and
  -> Outgoing SMTP: smtp-mail.outlook.com, port 587, STARTTLS, OAuth2.

Thunderbird successfully authenticates to Microsoft using OAuth2 for incoming email. However, when Thunderbird attempts outgoing email authentication, Microsoft's SMTP server rejects the authentication. The Error Console in Thunderbird records this message: "535 5.7.139 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Mailbox."

-> Refer to attached image: "Thunderbird Error Console_20260811.jpg". -> I am able to provide a short screen recording demonstrating the failure if needed.

To try and resolve the above, I completed the following actions:

1. Confirmed Thunderbird is current (153.0.2).
2. Confirmed SMTP is configured for OAuth2 rather than Normal Password.
3. Confirmed port 587 and STARTTLS.
4. Re-authorised the Microsoft account/OAuth connection.
5. Confirmed IMAP OAuth2 works.
6. Confirmed Outlook.com webmail can send successfully.
7. Reviewed Mozilla's current “Microsoft OAuth Authentication and Thunderbird in 2026” guidance, including the section covering cases where IMAP/POP works but SMTP does not.
8. Captured the SMTP failure in Thunderbird's Error Console.

However nothing worked, so I raised the matter with Microsoft support and eventually had the matter referred to their Tier 2 team. The Microsoft case number is: 7107041963.

Microsoft Support confirmed that for a personal Outlook.com/Hotmail account there is no user-accessible mailbox-level SMTP AUTH setting, and advised that SMTP is enabled by default for supported clients. However, because sending from Outlook.com webmail works, Microsoft Tier 2 declined to investigate the SMTP server response further and directed me to Thunderbird support.

I am able to provide a copy of the chat transcript if needed.

In any event, the TLDR version IMAP works using OAuth2, but SMTP using OAuth2 fails because Microsoft's SMTP server reports SmtpClientAuthentication is disabled for the Mailbox. Microsoft Tier 2 has referred the issue to Thunderbird support.

Questions:

1. Is this a known current issue affecting personal Outlook.com/Hotmail accounts using Thunderbird?
2. Is 535 5.7.139 SmtpClientAuthentication is disabled for the Mailbox known to occur with Thunderbird OAuth2 even though IMAP OAuth2 succeeds?
3. Is there a current Thunderbird-side workaround or alternative SMTP server/configuration recommended for personal Hotmail accounts?
4. Would changing the SMTP server from smtp-mail.outlook.com to smtp.office365.com be appropriate for a personal Hotmail account in Thunderbird 153, or should the current Microsoft-documented server be retained?

-> I note there appears to be conflicting advice on this point in previous support threads.

1. Given that IMAP OAuth2 authentication succeeds for the same Microsoft account, does this indicate that Thunderbird's Microsoft OAuth authorisation itself is functioning correctly, or could SMTP require a separate permission/token that may be failing?
2. Are there any additional Thunderbird logs or diagnostics I can provide that would help resolve this matter?

Disclosure: I used ChatGPT to help organise my troubleshooting notes and technical details for this post. The troubleshooting, observations and diagnostic information described above are from my own work on the affected PC.

A couple of days ago I was suddenly unable to receive email. I can still "Send." This may be relevant. A week or so ago my ATT email started requiring a verification process that required matching up figures. This continued for several days. Eventually I started receiving a "verification confirmed" message w/o having to match the figures and the log-in proceeded as usual. For the last couple of days I have not received the verification message and the log-in as proceeded in the normal manner. I remember a few years ago there was a problem with ATT and Thunderbird having to have a special pass word. It was called a SafeKey. Don't know if this is the same problem.

Since the recent update, 157.1, I cannot get the "Get Messages" button to work and it will not download new emails. I can download a previous version and it works just fine. I also cannot stop the auto updating function even though I check the box to not auto install.

I have lost mt SEND button when I want to send emails to others. This has resulted some time ago and is most inconvenient when replying to email's. How do I get it back?

Have been receiving alert notification that my hawaiiantel..net account is temporarily unavailable. My email messages to that account are not being received and I'm unable to move email messages to the inbox of that account. Have been receiving these alerts for the past 3-4 days. is there a way to resolve this problem?

My inbox appears empty. On the inbox setting it is only giving instruction to set up another account. My normal emails have disappeared. I can still see the emails on my phone however.

Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) mail.twc.com timed out. Try again.

New mail keeps going to either the Inbox, Notifications, or the Newsletter folders by default. No filters have been added to change the initial settings. How can the settings be modified so that all incoming mail goes to the inbox, eliminating every future instance of it being directed elsewhere?

I have no interest in the Notifications or Newsletter folders. I'm happy with getting rid of them completely, if that is a possibility that can solve the problem.

In the last couple days, I am not receiving messages in my email account inbox (att.net/yahoo). Messages are going directly to the local inbox folder. Windows 10.

When I search for new emails in the local folder, they are tagged with a gold diamond, and my option is to "Move to inbox again," which does move the messages back to the main inbox. But, "again" implies that the message arrived in the account folder, but got automatically passed to local folder. On or two occasions, I noticed an very fast dowloading to the inbox, which disappears immediately.

And, I get no response in my email account when hitting F5. F5 works for the local folder, and other accounts, and Shift-F5 (getting messages for all accounts) updates the others, but not my main email account.

The issue is not with att.net/yahoo. I have checked all my settings and server settings in Thunderbird, done the folder repairs several times, closed and reopened Thunderbird many times, deleted Inbox.MSF, etc., but nothing works. The issue seems to be specific to Thunderbird. Any ideas?

T-Bird consistently reports receipt of an email to be received one hour earlier that it was actually received. For example, I received and email at 4:03 pm (Windows 11 time and actual time). The time that T-Bird reports the email as being received is 3:10 pm. I would appreciate help in resolving this. I think it might be the cause of a problem with scheduling an appointment - the online confirmation says 3:10 is the appointment time while a confirming email (received moments later) says 2:10 is the appointment time

I keep getting this message: "We've identified a site certificate problem, trust for this certificate has been revoked." The location is "inbound.att.net" So I can't receive any E-Mails on my PC, but I can on my phone. How can I fix this?

On MS Win11, my TBird IMAP client (up to date) has two mail accounts. In one, deleted messages return immediately after deletion! Also, (possibly related), this account has TWO Spam folders (I did not do this). The other mail account's messages stay deleted and has only one Spam folder. I ran the re build tool on the first one without success. I am NOT technical, but have donated several times to TBird (I love it)