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Title: Thunderbird 158 – Outlook.pt (IMAP, OAuth2): Microsoft login page never loads, authentication error

Hello,

I can't connect a personal Outlook.pt account (outlook.com) to Thunderbird. The Microsoft sign-in page never appears and I get "Authentication failed".

Environment - Thunderbird 158.0 (64-bit), also tested on Beta; Windows 11 - Browsers installed: Brave and Chrome (Chrome set as default for testing) - Account: personal @outlook.pt, no Microsoft 365 subscription

Settings used - IMAP: outlook.office365.com, port 993, SSL/TLS, OAuth2 - SMTP: smtp.office365.com, port 587, STARTTLS, OAuth2 - Username: full email address

What I have tried - Account setup test says "secure connection to outlook.office365.com:993 established successfully". - Automatic setup: no login window opens; the Error Console shows GuessConfig trying SMTP on port 465 (NS_ERROR_ABORT) and then "authentication failed". - Manual setup with OAuth2 forced: a browser window opens, but it stays on the browser's start page. Once, instead of Microsoft, it showed a Google consent page ("Mozilla Thunderbird Email wants to access your Google Account") for a Gmail address I use elsewhere, even though I was adding the Outlook account. - Clicking links inside emails correctly opens the browser, so the default-browser association works. - Cleared saved passwords/OAuth entries for outlook/office365/microsoft; removed and re-created the account several times. - Created a brand-new clean profile: same result. Thunderbird Beta: same result. - Microsoft account "recent activity" shows no sign-in attempt, so the request seems not to reach Microsoft. - Main profile has extensions (LanguageTool, flagged as incompatible, and CardBook). Not yet tested in Troubleshoot Mode. - Error Console shows no OAuth-related errors besides the GuessConfig lines above.

Questions - Why would Thunderbird open a Google consent page when adding an Outlook account? - Is there a known issue with OAuth2 for Outlook.com in version 158, or a hidden setting that could cause this?

Troubleshooting information from about:support is pasted below. Thank you.

Trying to set up new Gmail account in Thunderbird. New account dialog opens, recognises Gmail address and imap details, but doesn't allow me to provide Gmail with password. Authentification failure results.

I had to change my Google password and I cannot get to my mail. I tried to uninstall/reinstall Thunderbird with no joy. When I try to open Thunderbird, Google responds: "The server cannot process the request because it is malformed. It should not be retried. That is all we know."

I am using Thunderbird 158.0 (64-bit) on Windows 11 and cannot connect a newly created Outlook.com email account.

The account works correctly through Outlook.com webmail, but Thunderbird consistently reports:

"Authentication error — Unable to log in at server. Probably wrong configuration, username or password."

I have spent considerable time troubleshooting this problem and have already completed the following checks:

Confirmed that IMAP access is enabled in Outlook.com.

Verified incoming IMAP settings:

Server: outlook.office365.com

Port: 993

Security: SSL/TLS

Authentication: OAuth2

Verified outgoing SMTP settings:

Server: smtp-mail.outlook.com

Port: 587

Security: STARTTLS

Authentication: OAuth2

Confirmed both usernames are my full new Outlook.com email address.

Confirmed that Microsoft lists "Mozilla Thunderbird" as an authorised application, with permission to read, write and send email.

Tested network connectivity using Windows PowerShell. Test-NetConnection outlook.office365.com -Port 993 returned TcpTestSucceeded : True.

Created a completely new Thunderbird profile containing only this Outlook.com account. The same authentication error occurred.

Tested Thunderbird Troubleshoot Mode without success.

Confirmed cookies are enabled and Windows is not using a manually configured proxy.

Removed saved OAuth2 credentials and retried authentication, without success.

Tested both external-browser and internal-browser OAuth2 authentication using mailnews.oauth.useExternalBrowser. Neither worked, and I restored the original value of true.

During an earlier attempt, the Microsoft authentication process displayed the error 127.0.0.1 refused to connect.

Microsoft's authorised applications page confirms Thunderbird has the necessary permissions, but Thunderbird still cannot authenticate. I have not successfully been prompted to enter my new Outlook.com account password through Thunderbird.

My existing Hotmail account works in Thunderbird.

Could this be a known Thunderbird 158 OAuth2 problem affecting newly created Outlook.com accounts?

As the usual configuration, password, permissions and network checks have already been completed, I would appreciate advice on identifying the underlying authentication failure rather than repeating those steps.

Thank you for your assistance.

I have multiple email accounts on Thunderbird (on MX Linux)... att.net, gmail.com and aol.com

While traveling without my computer, i had to reset my aol password on my iphone.

Now that I'm back at my desk, and being unable to find how to change the aol password on Thunderbird, I deleted the AOL imap account and have tried much of today to add a new AOL account.

In the past, I could create an 'app password' within AOL (browser) and use that password in Thunderbird... but that is no longer working.

Any guidance/suggestions?

I am running the latest Thunderbird version 140.17.0esr (64-bit) available in my MX Linux.

Been away for 1 week, and not used Thunderbird during absence. On return logged in as usual on desktop and cannot retrieve or send messages on Thunderbird - message asks for webmail password, which it has not done for many years, then will open inbox but only shows all mail up to the day I last shutdown the system (7 Oct), then continues to ask for password for host. Have tried editing password within settings (but it is correct anyway) and can separately log into webmail (using the same password). Essentially unable to use Thunderbird but unwilling to use email history and using the webmail interface (plusnet) is slow and unwieldy. Any ideas much appreciated! I also note that my Thunderbird version must have updated automatically on opening to the latest version -158. Could this be the problem?

I am using thunderbird to manage my email account. I want to add an existing shared email account from office 365 server. To get in it, it is necessary to sign with a password. Every time that office is requesting this password, thunderbird immediately hide it and send a message : "All is OK, you are connected" which is wrong... How can i avoid that thunderbird send this message and let me sign ? Attached is the message ( in french)

Haven't been able to get into Thunderbird since 9/26/26, every time I try it keeps asking me for my password. I key it in and it does the same thing. I have had someone to come up and look at it, but they weren't familiar with thunderbird, I have been having to use Kinetic email, don't like it. hate gmail.

I keep getting the following (see attached image) when I try to open my Thunderbird. I tried to unsuccessfully open safe mode because it still asks for a password from my very old BlueHost account. I previously worked with AI on this and deleted all BlueHost lines I could find in my account. View the image I have included and see all the messages that include BlueHost. They must be hiding somewhere in Thunderbird. I am not sure what version I have because I cannot open it. Please help! I be happy to send you my phone number is needed.

Hi, since beginning of October 2026 I cannot access my multiple AOL-accounts in Thunderbird under Windows 11. I am prompted to the AOL page, insert PW but at the end: "an error occurred". The PW is valid; I can log in to the aol-accounts on the AOL-homepage.

I already set all methods to OAuth2 and set usePrivatBrowser to true as mentioned in the forum; but it does not work. Any ideas?

Short problem description: Gmail auth is running before the master password dialogue

Long description: When starting up, Thunderbird runs Gmail auth before the master password dialogue. This leads to a failure of the login when the user does not enter the password in time. The access token is not unlocked, auth fails, and a browser window will pop up with the gmail authentication dialogue, necessitating further user interaction and generating extra mails because TB will be reconnected with a regenerated token.

Expected behaviour: Authenticating email accounts being delayed, until the secret cache is unlocked with the master password.

Since updating to TB 153esr from the previous esr, I occasionally get a server authentication error with imap.gmail.com. Most often they happen when first starting up, but occasionally seem to happen at other times. They seem to be transient as gmail works fine otherwise.

Just wondering if this is a known bug?

Hello,

There is apparently a bug in the latest release of Thunderbird, which has broken the callbacks for Yahoo! IMAP email using OAuth. Potentially, it may actually be a problem with Yahoo!, and how https://api.login.yahoo.com is attempting to reopen Thunderbird after logging in, as the process has changed. I've already reverted back to the ESR Thunderbird channel once, but on a recent update the issue was reintroduced. Screenshots are included.

Thanks for any assistance.

I had to reinstall Thunderbird after doing a clean install of Windows 11.

Since installing, the expected login popup for Gmail doesn't appear. I get the attached error message instead.

Yahoo worked fine after a few tries. What is the problem here, and how can I fix it?

How can I get rid of that horrible bug of Thunderbird prompting me for my login credentials. Already tried the following: re-adding my Email account, reinstalling Thunderbird from scratch. Nothing has worked.

I managed to add one email account, but now is impossible to connect any other, it doesn't matter if it's a gmail or a personalised email.

It says: Authentication error.

Unable to log in at server. Probably wrong configuration, username or password

both give me the same error.

Any advice?

Mozilla Account works normally directly inside Firefox, but logging into Mozilla Accounts through Thunderbird's Add-ons manager fails during the Firefox handoff.

Steps to reproduce: 1. In Thunderbird Add-ons, click Log in. 2. Thunderbird redirects to Firefox, showing "Continue with Mozilla account". 3. Click Continue -> Firefox displays "You could not be logged in. Please try again."

Troubleshooting already tried:

• Created a brand-new Thunderbird profile (thunderbird -P) — same failure occurs.
• Cleared cookies/site data in Thunderbird and cleared Firefox cache.
• Disconnected existing Thunderbird/Add-ons connections from Mozilla Account dashboard.
• Extensions and add-ons themselves install and download normally.