What version are you using?

Newest, standard. 146.0.1

Some exchange administrators do not allow access via IMAP. Has your admin made a change?

Have no admin. Just personal accounts: gmail and outlook. Is there a utility to check basic TB settings for suspect settings?

Have these accounts ever worked in Thunderbird?

Find out from your e-mail service provider what the incoming server settings and outgoing server settings should be for each account. You will need this information:

server name port connection security method authentication method username

Then ensure that all the settings in Thunderbird are correct. Incoming server settings are in account settings > server settings. Outgoing server settings are in account settings > click on account name > edit SMTP server.

Both accounts have worked for a long time. Probably been using TB for 3 or 4 years. Have struggled to get "real" incoming/outgoing settings for Outlook, especially. Microsoft isn't very consistent. Think I finally have correct information.

re outlook smtp sending

If you logon to microsoft account, it lists all the email addresses and calls them alias. How many mail accounts/email addresses are listed ? Is the problem outlook email address set up as 'primary'?

You can only send emails in Thunderbird using whatever email address is set up as Primary.

Other things to check: Firewall This might be controlled by the OS default or by an Anti-Virus you have installed. Access Firewall and make sure the Thunderbird program is set up 'allowed. Please confirm Thunderbird program is set up as default.

VPN Please check computer to see if a VPN has been enabled. Many AV's now off a VPN and in some cases it has been auto enabled. Please switch off VPN.

Localhost Outlook and Gmail both use 'Authentication Method =Oauth' To set up account, it requires use of the localhost, so if you use anything like Apache Xampp (often used by those who manage a website) then it needs to be switched off whilst creating the mail account.

In Thunderbird, cookies are needed to create the account

• Settings > Privacy & Security
• WEb Content
• Select 'Accept cookies from sites'

Have a reply as a .png, but website doesn't seem to want to upload it. Why?

Some people have tried to inser the image file into the forum text reply box - this is not possible.

Have you put the *.png image file into another document such as Word or a pdf etc? if yes, then it's not an image file, it's a document file. I've come across many people who do this - not sure why, but only image files can be uploaded.

Is the *.png image file stored on the desktop? Put the image file on desktop and then in this forum use the 'Add images' 'Browse' button to locate the image file and click on 'Open' to upload it.

Pretty sure I did that yesterday. Created message in Word. Used File Converter to change to .png (made 2 pages). Opened both in Digital image pro and concatenated them. Use forum uploader to upload them. Did that again today. Still won't upload. Little "clock" goes round and round without stopping.

Got another: Mozilla Thunderbird Thunderbird Authentication failure while connecting to server imap-mail.outlook.com. error a few minutes ago.

I'm just wondering why are you creating message in Word ? that process is very long-winded and unnecessary.

In this forum, you will see the message I sent to you. click on the 3 dot icon located to the right side and select 'quote'

This copies all my comment into the Test Reply box and then you can edit sections with your response - no need to use Word.

The images you copied into Word - just upload them to the forum. They are already an image file.

Alternative, if you really want to create stuff in Word - use the 'prt scr' key on keyboard to create a 'screenshot' of desktop. Select the area on screen and it's auto saved. In my Windows 11, the 'Pictures' folder contains the 'Screenshot' folder and screenshots are auto created as png files. Then upload the image. No converting, zipping or anything else etc.

Adding Thunderbird program to Firewall should rule out that as a problem. If VPN was enabled at time when TB attempted connection to server - that could have caused issue.

re : Authentication failure while connecting to server imap-mail.outlook.com.

I think it would be a good idea to post an image of your Account Settings > Server Settings Also post image of the outgoing SMTP server settings.

The first error message image you originally posted mentions 'microsoft exchange server' Yet additional image seems to imply this is a normal office outlook.com email address on outlook.com server. Are you using the correct server settings ? IMAP server settings: https://support.microsoft.com/en-gb/office/pop-imap-and-smtp-settings-for-outlook-com-d088b986-291d-42b8-9564-9c414e2aa040

Not sure where you are located but if outlook not working then check: https://downdetector.com/status/outlook/

Have you managed to get incoming ok for outlook and gmail ?

Created answer in Word because I thought it was the best way to maintain the formatting and make best sense. Have you managed to get incoming ok for outlook and gmail ? Yes, MOST of the time it works, but with intermittent errors.

Server settings are in upload.

Thanks. The server settings did not include Connection Security and Authentication Method. What have you got selected for those two: Expected: Connection Secuity: SSL/TLS Authentication Method: Oauth2

But have you got: Authentication Method: Normal Password

Everything I've read says use OAuth2. Normal password is in the Authorization drop-down, but I've been using OA2. Should I use Normal Password?

'Authentication Method: Oauth2' is the correct one.

If you had been using Authentication Method : Normal Password - then you would have needed to access webmail and create an app specific password just to use in Thunderbird - however that's not necessary. It just confirms the app password is not the issue.

However, I'm not certain why you are using incoming server name : imap-mail.outlook.com. Can you offer some explanation ? Have you just been using it for years?

Info on their website says to use this server name: outlook.office365.com Have you tried to use that server name for incoming ?

However, I'm not certain why you are using incoming server name : imap-mail.outlook.com. Can you offer some explanation ? Have you just been using it for years? Info on their website says to use this server name: outlook.office365.com Have you tried to use that server name for incoming ?

This has been a bone of contention for me. Have switched back and forth because find the definitive server addresses; they seem to vary with what webpage you look at. ChatGTP says: Correct servers in 2026 These are the only reliable ones now: Purpose Server IMAP outlook.office365.com SMTP smtp.office365.com Guess I'll switch to those. Thank you.