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Functionality and usability issue: I use the Thunderbird for Android app as an adjunct to my desktop installation. Recently I had occasion to reply to an email in Android to one "to" recipient and needed to add two "cc" recipients, but found no way to add the cc recipients without deleting the existing cc recipients and having to input the entire (dynamic) group again, but then was also stymied by that. How best to handle this issue?

Other than that issue, the lack of desktop contacts synching, and the lack of spam filtering, Thunderbird for Android has been a huge help, so thanks to the developers for their dedication and hard work.

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.

How to filter all incoming emails to copy to another folder?

Filter has no "on incoming" criteria, only

Subject
From
Date
Size

I want "upon arrival", copy to ... Archive will probably do.

Alternatively, is there a setting for ALL Subjects, ALL Froms, ALL Dates, ALL sizes?

Thanks.

Dear Ladies and Gentlemen,

the last few days my new mails didn’t arrive, perhaps because I tried to introduce new digital items. Please tell me how I can use thunderbird to get my mails; perhaps I have to change my settings. I find it strange that this occurs after I did a donation to you….

Regards,

Agnes Haffner

Hello, when I try to answer a message or forward an e-mail, both the attachment, send and more options buttons are missing. They are there when I compose a new e-mail. What can I do?

My recollection is that prior to a recent automatic update to Thunderbird 140.12.1esr (64-bit) when I had a message composition window open, there were "SEND" button and possibly a "SEND LATER" button (to the left of the addressee and cc addresses in addition to the keyboard shortcuts (CTRL ENTER and CTRL SHIFT ENTER).

Following the update, there is no longer anything to the left of the addressee information. I have checked the toolbar menus, and there do not appear to be any button options. I can still send messages, but the lack of the buttons is a hindrance.

Thunderbird 152.0.1 Windows 11 Pro 10.0.26200 Build 26200

When I create a new e-mail or reply to one that I have received I am able to type in all fields, but there is no "Send" button to the left of the "From", "To", and "Subject" fields.

I can work around this by clicking "File...Send Now", but that is very inconvenient when I am sending many e-mails.

A "send later" button came up one morning instead of the usual "send" button. When I clicked on the write button to see where the "send" button was, several choices came up but when I clicked on the "write" choice I lost the other choices and now can't get back to the original write button and still no "send" button appears anywhere on the menu. I can save messages to Draft but still can't actually send them. I can still receive emails, just can't send them! Help!

After updating to 153.0.1esr(aarch64). the SEND button has disappeared. There's no way to send an email. (I can receive emails.) I am a Mac mini M2 Pro. OS 26.4.1

I cannot find a link to download a previous release of Thuderbird, which was working fine until this update.

After fixing the view problem of my email in Thunderbird (thanks for the F8 tip!), my email stopped downloading. I have no "prompt for password" checked. There isn't a primary password checked. I've confirmed the pop outgoing email is correct with the email provider (google). I can get into it without any issues and see my emails there.

I've re-entered the password for the pop outgoing email to no avail.

I have used Thunderbird on a MacBook Pro Max M4 for a while now. It worked fine until starting last Monday. Ever since then, I have to go to 1&1/IONOS e-mail on the web to send e-mails or use my iPhone and blind copy myself. It’s a pain going back and forth.

1&1/IONOS tech support helped me make sure all settings for the outgoing server (smtp) were and are correct. Tests on both incoming and outgoing ports are successful in the Thunderbird settings, so I don't understand why my e-mails are not sending. I have no problem receiving e-mails on Thunderbird. This problem on outgoing e-mails applies to both text-only e-mails and e-mails with attachments. Screenshots are attached.

There is 17.9GB worth of data. Do I perhaps need to delete some of it? I archive old e-mails offline once a year, generally in January for the previous calendar year.

Thanks, Tim

My big computer seems to be shut out of thunderbirds but my phone still works now that I contacted spark my phone now no longer works as well. please re-enstate my thunder bird emails onto my big computer and my phone. I prefer thunderbirds than using the xtra.web page. thankyou for your time on this. Janine van Marrewijk.

I changed my password for Greenby/Plusnet today. Now Thunderbird is unable to connect to them. The password is correct as I can enter website directly. No problems before change. Grateful for help.

Should I reinstall?

I have version 153.02esr. Since two days ago I cannot reply or forward messages. It pulls up the appropriate page but there is no box to send, the space is just blank in the upper left hand corner.