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As of September 3, 2026 all my new emails are going into a random folder instead of the inbox. This is also happening on my wife's PC plus and we are not getting the emails to our iPhones until we get out of Thunderbird. What has changed? This has not happened before.

Thunderbird has always had a problem with filtering all incoming mail to the correct folders. Sometimes it does it correctly and sometimes it doesn't. But this morning it is dumping all my incoming mail into a folder that isn't the Incoming mail folder.

How do I get it to put the incoming mail in the Incoming folder?

This started almost two months ago. When I open my email on Thunderbird, the inbox fills OK. As I go through the emails at some point, several just disappear from Thunderbird? When I access my emails directly from Spectrum, they are still there, but if I refresh they may disappear.

I paid an expert on Just Answers and he spent over an hour and came back with Spectrum was having issues, they were aware and they were fixing them. I thought the problem was solved, but then it kept on happening. I am losing important documents every day! Please help me!

My husband (DG) is 88 and beginning to have severe memory & analysis problems. I recently tried for three days, using his computer, to set up an account for him on the Social Security site, that I could oversee. It accepted a password, but kept asking for a 'backup code' that supposedly was 'assigned' - so I would have a second method to verify the account. There was no way, on that web page, that I could request a 'backup code' or ask for the '10 backup codes' that were supposedly given automatically. I wanted to simply get a letter that explained his SSA eligibility, so we could apply for Senior housing. I was able to call SSA and request the letter - but it will take 14 days by mail. We need it now - and I should have been able to simply download a PDF eligibility letter to print out. In less than 5 minutes, I was able to request and download an eligibility letter for myself on MY SSA account - but could not do it through his SSA account. I need to be able to communicate with SSA (& other agencies) and receive their replies through an email "AccountForDG@centuryxxxxx.net" that I can read in my email account "CuriousQuestor@centuryxxxxx.net). How do I set this up? Thanks in advance.

I am unable to send Email. I am using THUNDERBIRD app..My Email address is [redacted from public] @talktalk.net. I am receiving mail but cannot send.. I have a message that reactivation is required after being blocked. [ have paid my subscription but still blocked. Thunderbird version 155.0

Thunderbird demands my password for outgoing SMT server when I go to send an email but when I enter it, system won't accept it even though it is the correct password. I have had this problem for some time and it comes and goes. Sometimes I have ebeen able to send without a problem, then it comes back I had a helpful reply from this forum (can't find who posted it - Mick?) tellling me to go into the error console (Ctrl + Shift + J) and delete eveything in that. I tried that. It worked at first, but now when I do it, it has no effect. And the problem now appears to have become permanent, although occasionally after I have been working for some hours, then suddenly I can send without any problem. Problem hasn't budged though for a couple of days now. This is a mysterious and erratic gremlin, which now seems to have taken root. Any suggestions please? Carol

When I send an email with my HTML file signature Thunderbird appends a text signature as well. The text signature is not visible in the draft email, and is not in the settings. The text signature is added for separate identity with no signature enabled. I want to stop this. Any ideas please?

no access to email through Thunderbird since aug. 20th. Spotty. Use spectrum and they seem not to be interfacing with Thunderbird. Will this end? Know we are not the only ones.

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.

I receive emails, but can`t send any, there`s the note: Sending the message failed. An error occurred while sending the message. Mail server response: SPF ERROR - see page / SPF Error: Please see http://www.openspf.org/Why?id=kubtrans.justyna%40o2.pl&ip=83.30.162.147&receiver=smtp.wp.pl. If you are a poczta.wp.pl user, check the SMTP authorization. / If you are a poczta.wp.pl user, check the SMTP configuration: http://poczta.wp.pl/autoryzacja/. Please verify that the email address is correct in the account configuration and try again.

How can I fix it?

for a week or so now, I get the following message when trying to send" Sending of the message failed. An error occurred while sending mail. The mail server responded: Transaction failed Reject due to policy restrictions. For explanation visit https://postmaster.gmx.net/en/case?c=hi&i=ip&v=149.102.242.95&r=1Mirna-1wPNAF1v2y-00h7M4. Please check the message and try again."

receives fine, will not send