Thunderbird Community Forum

All was well until about six months ago. When I try to connect to my provider TB won't connect. BUT. At other times it will connect then every few minutes will try to connect again - then again .... I get this message "Connection to the server mail.comcast.net timed out". Then I get this message each time it fails "Login to server mail.comcast.net with username 170834000 failed". It keeps asking me to input my password even though everything is working appropriately. Then at other times it says it doesn't connect but it has connected and it still continues to ask me for a password.

I have uninstalled TB and reinstalled it thinking that would fix it - it didn't. I have changed my password - again to no avail. I let TB choose where to put things and configure each item appropriately. I don't try to get in the way of what works.

Comcast is apparently getting out of the email business and asking everyone to move over to their chosen substitute (Yahoo.mail) and I have not chosen to migrate at this point. Maybe that's the problem. This is the message I get each time I log into Comcast.net:

"A better email experience is now available for you

You're invited to upgrade your email account to Yahoo Mail, so you can enjoy a more user-friendly experience. Your email address, messages, folders, and contacts will not change.

With Yahoo Mail, you'll enjoy enhanced security, a built-in calendar that's easy to use, AI-powered inbox organization, and a top-rated mobile app for easy access on the go."

I am not aware of any changes in the settings from before when it was working well and now when it seems to be erratic.

I am not terribly computer savvy, but I'm usually able to trouble shoot and fix the issues that confront me. This time I'm out of my league! I need help.

Thank you for helping me.

I prefer to have the Contact Name only display in the TO: field of composed or outgoing emails. I already know their address is correct in my Address Book, why do I need to see it? Presently, the TO: field shows "Name <email address>", as shown in the first uploaded image.

I am a new user to Thunderbird and I have reviwed, and believe, set all the Settings correctly that I could find on the subject (see second uploaded image), but the results do not change.

What am I missing?

Thanks Matt T

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.

Please excuse the length of this but it's necessary.

Began using Thunderbird (TB) in June, 2026 accessing email from wowway using POP3 (I know not imap, but old habits die hard). Changed password on wow in July and changed it in TB. Thereafter, and up until yesterday, TB was unable to logon to wow. However, the new PW allowed access to emails by browser logon to wow; old PW failed as it should. Frustrated with not being able to use TB with new PW: - deleted AppData/Roaming/Thunderbird folder (profiles and all) - recovered a backed up copy of TB folder from mid June when things were working and copied it to AppData/Roaming. Bingo, was able to get and send emails. Puzzled, looked at TB Saved Passwords and verified the old PW was being used. To verify this, I sent an email to myself, pressed F5 to get mail and it was in the inbox, and also on wow server.. BOTTOM LINE: There is no question that TB is using an old, changed wow PW. And if PW in TB is changed to new PW, access to wow fails. How can this be? Help please.

There was an earlier Case with the exact same name as what I named this case which was archived back in 2025. I have been living with this same problem since last year also. In the previous case there was reference to "downgrading" to an earlier version of TB, but there have been a bunch of updates since then so I doubt that would fix my problem because that earlier version is now over a year old.

I have one Gmail folder that correctly has one folder label "Junk." However, I have 4 folders that are AT&T related (2 from the domain "sbcglobal.net" and 2 from the "att.net.") For some reason when I set these folders up years ago they started out as labeled "Spam" instead of "Junk." Of those 4 folders 2 of them have the duplicated "Spam" folders, one from each domain."

When I go to Folder Properties I see "imap://XXXXX%40sbcglobal.net@imap.mail.att.net/Junk" on one of these Spam folders and "imap://XXXXX%40sbcglobal.net@imap.mail.att.net/Bulk" in the other. And the same "Bulk" vs "Junk" issue is in the other domain as well. All are named "Spam."

Can I simply delete one of these folders that are named "Spam" in each domain? Does it matter whether I delete the one ending in "Junk" or the one ending in "Bulk?"

Thanks.

I want to copy my windows Thunderbird profile to Linux but my Profile Directory will not open when I press open directory. I downloaded Thunderbird from the Zorin app store, and it may be a flatpak or something – it won’t tell me now because I have already installed it – but I believe that could be a reason for the directory not opening. Is there a non-PC-literate way of finding out and fixing this?

just got Thunderbird, i added my outlook email then got to the "connect your email setting" then i clicked continue cause i wanted to use imap and got a "Authentication error". I got Thunderbird on a different device and used my gmail on that device and it worked fine. Only get the error when i try to use my outlook email and i don't know what to do.

Hi.

Just had a not requested update to 153 esr, which in itself is generally fine, with a small exception.

The windows min, max and close buttons all come up with a code.

Probably just some weird setup I have but any ideas will be welcome.

I use userChrome.css to give a background colour, so maybe the ID of each has changes for any css

1. titlebar-min{height:1.66em; background:#00b !important}
2. titlebar-max{height:1.66em; background:#090 !important}
3. titlebar-close{height:1.66em; background:#d00 !important}

but I don't see how that would effect the actual bare icon

Thank you

My eyesight5 is pretty bad. I'm trying to make the display fonts quite large (32), but nothing seems to be working. The settings allows me to select a font and set the size from a pull down list, but nothing changes. Presentation and functional operation should be isolated from each other as possible.

Hi, It worked flawlessly in the previous version. In version 153.0.2esr (64-bit), I can't drag and drop messages to a folder (e.g., Desktop). Does anyone have any ideas on how to fix this?

I went to View and tool bars... Composition was already enabled. Alt and F10 did not reveal "Send." I tried to use the "Customize" menu and it did not include "Send." I do appreciate your help, even if everything suggested so far has not worked. My fear is that I may have to delete my Thunderbird in its entirety and re-install. If I do this, is there a way for me to save my address book? Is there still a way for me to get my Send back.

I may have to just settle using <Ctl> Enter on my keyboard. Bill

The SEND button has vanished in Thunderbird. I don't recall changing anything or performing any updates, though my memory is getting to be unreliable.. In addition, the LINK button has vanished as well. I imagine I did or am doing something stupid and it's an easy fix, but what that might be totally escapes me..

Thunderbird stopped retrieving mail from one of my accounts, does not give an error message, just says no new emails, Outlook and other devices are continuing to retrieve from this account with no issue. So the issue is with Thunderbird. Is there a text or phone number I can use with tech support to clear this issue? I checked with AI Bots to resolve this and it seems quite involved.

Thank you. Rafael

1) How do I get the emails Thunderbird marks as spam to be moved to the Spam folder without me doing anything. I have thousands of emails now most marked as spam but I have to go in and move them one by freaking one!

2) Also you freaking filter system doesn't work worth a crap! I have created filters for instance: for any emails that have @cypress.com in the From part of the message to be moved to a folder under my inbox named Cypress. I have run it many times and actually none of the filters I've created work? They are very simple to understand and I am doing them correctly as far as I can tell but they don't work. I have created at least a dozen filters and the only emails moved are ones I moved manually myself.

And this training crap you have I don't know what you think it should take a computer to learn to move something to a folder. It's not like a child that has to be taught how to spell. You tell it if it has this in whichever field you've selected then it should move it. Not have to be taught? Not a bright idea in my opinion. It's why AI isn't very smart at least what they release to general users. Anyway I digress.

If you can help me with the above issues in the above paragraphs 1 & 3 I would greatly appreciate it.

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

Hi using 153esr and Win11

I have my emails on an encrypted drive. Until now if I closed Thunderbird I would have to enter my Master/Primary password before and emails would show, i.e they were protected from casual view.

Now if I type [cancel] at the request for a password, twice in a row than all my emails are visible.

I though it may be this new thing where the [close] icon functions differently, but even if I close via the menu File > Exit it seems Thunderbird still has access to my emails without authorisation.

Any ideas would be useful

Thanks