Maybe it will help one or the other person concerned. Settings -> General -> Edit configuration I can confirm that the workaround described there for Thunderbird works for me, namely in Thunderbird via. Volko also referred to the Microsoft Answers forum post Thunderbird IMAP responded: User is authenticated but not connected, where, where the solution can be found. Īs it looks, the error only occurs when accessing the office365 email servers via IPv6, so it does not occur with a pure IPv4 internet connection. In case you haven't heard it elsewhere, here's a short info about a 'capital buck' Microsoft shot regarding Outlook between the years:Īfter the announced deactivation of Basic Authentication, suddenly, despite using 'OAuth2' as authentication method, the access with Thunderbird via IMAP to my business (Office365) email address was no longer possible, I went troubleshooting. Problems accessing office365 email servers via IPv6 + workaround. Volko wrote (I've translated the comment): emailed me and also addressed the Thunderbird Exchange Online login issue. Reader report #2: Thunderbird fails with oAuth2 Theo referred to the Microsoft Answers forum post Thunderbird IMAP responded: User is authenticated but not connected, where the topic is discussed. This advice to disable IPv6 brought success. The tenant admin says the license is active and IMAP is allowed.īlog reader Theo gave the advice to switch to oAuth2 after all and if there were problems, try the flag: Since the day before yesterday the IMAP access with Thunderbird to a MS365 account is not working.Įrror message: User is authenticated but not connected. Within my German blog reader Klaus left the following comment, reporting issues with Thunderbird IMAP connection since the end of 2022 (I've translated the comment). Reader report #1: Thunderbird fails with oAuth2 The issue was brought to my attention by two readers.

However, there is the problem that the IMAP connection to Exchange Online via oAuth2 in Thunderbird is on strike. IMAP connection goes on strike in Thunderbird This means that all clients that want to access Exchange Online mailboxes via IMAP will have to switch to oAuth2 (Modern Authentication).

In the article Reminder: Basic Authentication in Exchange Online will be switches off in 2023, I pointed out that Microsoft will finally switch off Basic Authentication in Exchange Online at the turn of the year 2022/2023.

Thunderbird oauth2 office 365