Thunderbird Community Forum

bob.fannon

Feb 14, 2026, 13:01 CST

I have used Thunderbird for a number of years with Plusnet (using POP settings) in the UK. However, Plusnet has transferred their support to a company called Greenby who have made a hash of it and offer very poor support. So, I want to use Outlook as the mail server but I am unable to send any messages via Thunderbird to the Outlook server. I can however download messages with no problems. The error message I get is :- Sending of the message failed. Unable to authenticate to Outgoing server (SMTP) smtp.office365.com. Please check the password and verify the 'Authentication method' in 'Account Settings | Outgoing server (SMTP)'

My default Outgoing Sever settings are :- Server Name : smtp.office365.com Port: 587 User Name: bob.fannon@outlook.com Authentication method: OAuth2 Connection Security: STARTTLS

I have tried deleting the Thunderbird account and re-creating it but still got the same result. I also tried to use my old Icloud account ( having first setup my App Specific password) but got the same result.

Guten Tag, ich habe meine Yahoo Emails alle erfolgreich auf Thunderbird übertragen. Danke dafür! Nun möchte ich bitte thunderbird als Standard Email und NICHT mehr yahoo. Wie lautet meine thunderbird Email für Visitenkarten usw.? Yahoo soll bleiben aber nicht mehr als erstes Email Programm. Ich möchte auch yahoo emails löschen, die dann aber bei Thinderbird erhalten bleiben! Wie stelle ich das an? Im Moment sind beie email Programme ein zu eins verknüpft. Ich möchte bitte nur noch mit Thunderbird primär arbeiten und benötige dazu eine Email Adresse. Kostenfrei. Also OHNE Kosten! Das ganze auch aucf dem iohone. Mein Mac Book hat es schon Ganz ganz vielen Dank

Coming from https://support.mozilla.org/en-US/kb/cannot-send-messages, and https://support.mozilla.org/en-US/questions/1596545#answer-1837376 (thank you christ1)

Account settings attached. I don't have an active firewall. My email provider is microsoft (outlook) No antivirus installed Linux Mint 22.3 x86_64 Thunderbird 153.0esr

I have confirmed with microsoft support that the ports and such are correct, they claim thunderbird is the problem.

My folders are in disarray and it is cutting into my productivity to file emails. I have tried but it in settings but it doesn't work. Many are in alpha order but there are 2 different two different sections of the same name, and some odd files end up in an alphabetized section.

For instance there are 2 different ZBV sections with other stray folders in the same area that should be in there own alpha folder area. It's a mess to find the right folder. I have to scroll up and own and look for the folder I need to file in. I would be happy to donate, and i have in the past, but I really need this to get fixed. Please, please, please...

TB suddenly moves messages from inbox to trash automatically without any interaction. Search through the forrum shows that it has been asked for already, see https://support.mozilla.org/en-US/questions/1588804, similar postings can also be found with you search engine.

As described in other postings, the messages are moved from Inbox to trash. When moving them back manually from trash to inbox, they are moved to trash again immediately.

• it happens for the default account only,
• there're no filters at all in TB,
• junk detection is disabled,
• Settings->General Storage is all disabled,
• (account)->Settings->Server Settings has checked "move deleted messages to trash",
• (account)->Settings->Storage is all disabled,
• Inbox->Properties "Repair folder" does not help,
• Inbox->Properties "rules is set to "use account settings" (and greyd out "do not delete messages"),
• exactly same behaviour when starting TB in save mode,
• manually deleting all *.msf files (for inbox) does not help,
• manually deleting xulstore.json does not help,

Additional notes, which are not related to the problem, IMHO:

• IMAP on port 993,
• no other clients anywhere are connected to that account,
• TB configured for more than 10 accounts, more than 500 folders and sub-folders,
• host with > 16GB RAM, TB uses 3GB virt,
• problem observerd in older TB also, at least 13x.x

I'd be happy to debug/trace the problem if someone can give me detailled insructions how to start TB with debugging. Please feel free to ask for about:config settings as they are non-ambiguous and language independent ;-)

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

Hi,

I'm running the latest version of Thunderbird 140.12.1esr on 15.7.7 (24G720) on an M1 processor.

I'm witnessing Memory leak > Thunderbird who usually use 800MB jumps to Gb up to 60Gb

It makes this version unusable.

Here is a loom of the incident: https://www.loom.com/share/0b8e661b42d64d749d80adfd71fd1e04

+ a screenshot

Anyone can help ?

Best Olivier

When messages arrive in inbox and are marked spam they do not auto move to spam folder. I have to uncheck the spam icon and re-check it. Not until then will they move to spam folder.

Martha

I have not being able to add this 4 account to thunderbird: hotmail.co.uk/ live.co.uk/btinternet.com/gmail.com. I keep getting error either cannot connect to server or username and password wrong. I have managed to add two accounts successfully. I don't quiet understand what is happening with this new 153.0.1 version. I has it working before I had to reinstall windows 11 PRO. Could you help me please! Thank you! Best regards, Jairo Goncalves

thunderbrd version 153.0.1 64bit windows11 Spamfilter problem

my contacts are all in the personal address book convinced they get filtered as NOT SPAM, recently some addresses out of my adressbook get filtered anyway - weird an expert told me to setup a whitelist as a subfolder: I did but same prob... as far I know the address book works like a whitelist anyway, no success also not long ago thunderbird had an update - and it feels since the dodgy filtering started. Using thunbderbird for ages - never had that prob ever - till recent

Is there any known solution please ? Thanks & regards Jochen

I can see that there has been a reply or a messages was forwarded and when I right click for the menu "Open" may not even appear at times. When it does appear "Open in Conversation" is not always presented as an option even though there has clearly been conversation as I can locate reply's in the Sent folder. Sometimes it's there but when selected it opens a tab that only shows the email and none of the conversations. It's hit and miss and I can find no rhyme or reason. Any help would be greatly appreciated. Also, I would love to Testflight Thunderbird on Apple. Thanks, Sue

In recent update several duplicate folders were installed in three different email accounts. Point to them there was a 'delete' button enabling elimination of duplicates. However, on two accounts, 'Drafts' duplicates didn't have the delete button enabling elimination. How to clean up?

I ran TB in troubleshooting mode and the problem was still there. I deleted the account and created it again but it did not help. I killed TB and restarted, no joy. I rebooted Windows (build 26200.8875), no help. I have a working hotmail account so I compared the Account Settings and Server Settings, they are identical. Both accounts can contact the Mail Server and I get the Certificate ok. I could add the hotmail email account to my Mail app on iPhone and iPad and that worked fine, so seems like a Windows Thunderbird issue. I tried changing the password of the account to the real password but then restarting TB I got an error message: "login.microsoftonline.com needs you to confirm access again to keep syncing with your account. Username: <foo>@hotmail.com". I do not know how to handle that.

In sending a new email, when I go to enter the "TO," various email choices pop-up - but not all are correct. How can I add and/or correct those popup choices?

BTW, I have a screenshot. How do I get it here?

Hello, I started using Thunderbird in order to be able to manage all my email accounts from one place and I stumbled to one problem. I have 6 different email accounts and all are created by me.

I know that I cannot add a Proton account as it requires a paid service from Proton that I don't need as I use it only as a backup account in order to be able to recover the other 5 ones.

My Yahoo account added successfully without any problems as my 2 Google ones.

My primary outlook was added successfully by using the simple add account setup. The problem started when I was trying to add my second outlook account. Everything I tried it always gives me an error that says "Authentication error. Unable to login at server. Probably wrong configuration , username or password." I know for a fact that the username and password are correct as when I start to add the account it displays a prompt on my phone to verify the connection. But at the last step it says the error I mentioned. I even tried to clear all cookies and passwords and tries again but without any success. I compared the configuration of the 1st outlook one to the 2nd and they were correct. Correct hostnames, security etc.

I also checked the account settings in of the emails on the providers page and the only difference is that in the 2nd I haven't enabled the 2FF authentication.

What am I doing wrong?

Appreciate the help! Alex

Been using outlook since 2000, I am tyrin to cut the umbilial cord to outlook as it is craper each year that passes.

Can i have more than 1 sig as i use maybe 10 different sigs for different reasons?

I see a use file do i get to choose a differt file when inserting sig or am i stuck with one and have to manualy change file or copy from somewhere else.

Once i get Thinder runnin i wil be happy to support on a monthly basis but i need to se if ti will suffice.

The email I thought I’d sent isn’t in my sent folder. I saw it being sent. I also tried restoring the sent items folder, but it didn’t work. What should I do? Is there any risk of it being misused?