Thunderbird 102, Microsoft 365 and POP stuck fetching emails

[scplyr]

Hi All,

We recently moved from gmail to microsoft 365, and we are running TB 102.4, and we use POP.

We noticed two issues:

Emails take a lot longer to download on microsoft than on gmail. Email would often get 'stuck' downloading a single email for more than a few minutes. Email is often just plain text or several hundred KB. It's not an internet issue as downloading from gmail was lots quicker.

Downloading emails via POP would often get stuck mid-way and no longer continue. These are totally random emails and are not large or different in any way. Using different ISPs has not fixed the issue. Email in the status bar would get stuck "Downloading message x of y" and no longer continue. A reboot and recreation of the account does not fix this. Thunderbird gets stuck downloading the same exact email again. We have encountered this across multiple users as well

Issue #1, we can wait around it, but not with issue 2 wherein I'm forced to have the user move to IMAP (which does work).

Our MS365 is totally bone stock with the exception of allowing POP and IMAP in the permissions.

This problem is quite random and doesn't seem to be a client side issue either. All are running Windows 10 64bit and use the 64bit version of TB.


Server settings as suggested by MS:

POP outlook.office365.com / SSL/TLS / OAUTH2 / Port 995

SMTP smtp.office365.com / STARTLS / OAUTH2 / Port 587

Am I the only one encountering this? Is there any current workaround?

Thank you!

[DanRaisch]

Were these MS account set up new when leaving Gmail or had they been in use previously?

Try changing the authentication method for POP and SMTP and the port number for POP:

POP outlook.office365.com / SSL/TLS / Normal password / Port 993
SMTP smtp.office365.com / STARTLS / Normal password / Port 587

You will have to clear stored OAUTH tokens for POP and SMTP so that the server will ask for a new password.

[scplyr]

Thanks for this.

These accounts were created new on Microsoft 365, then had the emails synced to them with MS's migration tool in the exchange admin site. Apart from copying over the emails, the accounts are not edited in any way except to add the permissions of using POP and IMAP.

Also, tried just now your suggested settings with the thunderbird config -- it gets stucked "checking password".

Tried using different combinations of the port number and which authentication to use like
Port 993 + OAUTH2
Port 995 + Normal authentication

All other combinations except for Port 995+OAUTH2 would result in getting stuck at 'checking password', and the popup from microsoft asking to key in the username and password would not appear.

Thank you!