Thunderbird Community Forum

My personal Outlook.com account can receive emails normally through Thunderbird IMAP, and sending emails through Outlook.com webmail also works.

However, SMTP sending in Thunderbird fails even though Microsoft OAuth2 sign-in completes successfully.

SMTP configuration:

• Server: smtp-mail.outlook.com

• Port: 587

• Security: STARTTLS

• Authentication: OAuth2

Thunderbird's Error Console shows:

• 535 Authentication unsuccessful

• Error during AUTH XOAUTH2

• 500 Unrecognized command 'Length: 7'

I have verified the settings and refreshed my OAuth2 credentials. The error persists.

This appears identical to Mozilla Bugzilla issue #1917321.

I contacted Microsoft Support (case #7111097598), but the agent referred me to Thunderbird without confirming whether SMTP AUTH is enabled for my mailbox.

Could someone help determine whether this is an OAuth2 configuration issue, a Thunderbird compatibility problem, or a Microsoft-side SMTP restriction?

Hi,

I've started experimenting with Vibecoding some extensions for myself.. But I keep hitting a problem where TB reports back that folders are stale.

Specifically I'll hit something like this:

[Exception... "Component returned failure code: 0x80550005 (NS_MSG_ERROR_FOLDER_SUMMARY_OUT_OF_DATE) [nsIMsgFolder.messages]" nsresult: "0x80550005 (NS_MSG_ERROR_FOLDER_SUMMARY_OUT_OF_DATE)" location: "JS frame :: resource:///modules/ExtensionMessages.sys.mjs :: getMessagesInFolder :: line 925" data: no] ExtensionMessages.sys.mjs:928:13 [Exception... "Component returned failure code: 0x80550005

Usually when I go look at these folders in the UI, the total-email-count for the folder in blank, but the Size of the folder will show >1kb (eg .. something greater than zero). If I click on the folder, TB updates the summary file and all is well, for a while.

Some folders do report as no messages, and "blank" for file size as well.. but those seem to be genuinely empty.

These types of issues are causing pain in several extension ideas I've had, and I can't seem to figure out a way to handle them.

For example: I had an idea to create and extension to delete empty folders. The original version would encounter these NS_MSG_ERROR_FOLDER_SUMMARY_OUT_OF_DATE folders, and then just wipe them out as TB told the extension there were no emails in it. I found this out a little too late for some folders..

Another idea was to create and manage Virtual Search folders automatically. But I've hit a similar issue there with this staleness and had to skip such folders.

I've tried to get the extensions to trigger rebuilding summary files when we hit this error, but that never seems to do the job. The only method I've found is to open the folder manually in TB. Sometimes I'll find that starting a Search across the folders also helps - but that also tends to bail out unexplained.

I'm working with a lot of emails and folders..

If anyone can help explain why TB "forgets" whats in a folder, and how to trigger a summary-rebuild for a specific folder I'd be interested in hearing it.

Thanks

Hi,

For both servers imap.exmail.qq.com / imap.263.net, when I click on the email subject in the email list during downloading processes (many emails headers are being downloaded but email body downloading is not completed), the email is broken without any content (only header).

I go to the web email server and move the email to another folder and then move it back to inbox. Then I delete the same email in Thunderbird and donwload again the email again, it's completely downloaded with the email body.

I don't have any issue with eM client or Outlook for such issues. Any possible setting to solve this issue?

Thanks.

When I attempt to send an email in Thunderbird I get an extensive string of gibberish that I have to delete before I can send the email. What can I do to get rid of this huge irritation? Thanks

My e-mail stopped working a week ago. I get as far as "connecting to IMAP but then get a "Login to server imap.orange.fr with username [redacted]@orange.fr failed" message. I have changed the IMAP and SMTP passwords several times but none seems to work. What am I doing wrong?

My spam folder has remained empty for the last 2 weeks- also, wasn't the folder called junk before? Its now labeled Spam and remains empty. The spam is just gone and not going to my regular email either. Please help.

I used to access my emails through the pop server however after an update there were weird things happening and somehow I managed to get my emails through the imap server. When I tried to get it back to the pop server, the default button was greyed out.

Today I have deleted the imap server, thinking that it might allow me to use the default button for the pop server however it is still greyed out.

When I went in to try to set up email on the pop server it is telling me that I already have the pop server but it isn't the default and I have no way of getting any of my emails now.

HELP!

Dzień dobry od dłuższego czasu (tygodnie) mam problem. Kiedy ktoś wysyła do mnie wiadomość, na koncie wysyłającego pojawia się automatyczna odpowiedź zwrotna zawierająca nieznany, niepożądany adres mailowy :officebackup.chk@gmail.com. Niezależnie od odbiorcy wiadomości, wszyscy otrzymują tego typu wiadomość, jak poniżej przykład: Przykładowa infromacja: Temat: Mail delivery failed: returning message to sender Data: Wed, 28 Oct 2026 14:19:34 +0100 Nadawca: Mail Delivery System <Mailer-Daemon@da2.fantex.pl> Adresat: prima@fan-tex.net This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

officebackup.chk@gmail.com host alt4.gmail-smtp-in.l.google.com [172.253.158.27] SMTP error from remote mail server after RCPT TO:<officebackup.chk@gmail.com>: 452-4.2.2 The recipient's inbox is out of storage space. Please direct the 452-4.2.2 recipient to 452 4.2.2 https://support.google.com/mail/?p=OverQuotaTemp 41be03b00d2f7-cdad55fbfd5si6228338a12.395 - gsmtp: retry timeout exceeded

Jak pozbyć się tego adresu z poczty? Uprzejmie proszę o pomoc. Z poważaniem Robert