8 July 2025, 05:04 PM
[*]Microsoft has turned off old login methods (basic authentication), so Thunderbird not work with Office 365 if you’re still using them.
[*]Using wrong server details or wrong settings will stop Thunderbird from adding your Office 365 account.
[*]If you have 2-step login and don’t use an App Password, normal passwords won’t work.
[*]Sometimes, Office 365 blocks IMAP or SMTP, which stops Thunderbird from working.
[*]Firewalls, network blocks, or using an old version of Thunderbird can also cause problems.
The Manual Ways to Fix This Are:
1. Cross-check the IPv6 Settings
Sometimes Thunderbird struggles with IPv6 connections. If you face connection issues, try disabling IPv6 in Thunderbird’s advanced settings to force it to use IPv4 instead.
2. Try to Reconfigure Your Thunderbird Account
Remove the existing Office 365 account from Thunderbird and add it again from scratch. This helps fix any incorrect server or login settings and ensures OAuth2 is used properly.
3. Change the Authentication Way to OAuth2
Switch the authentication method for your account’s IMAP and SMTP settings to OAuth2. This allows Thunderbird to connect securely using Microsoft’s modern login instead of outdated basic passwords.
4. Install the Updated Thunderbird
Make sure you’re using the latest Thunderbird version — updates fix bugs and add support for modern security protocols like OAuth2, which Office 365 needs.
What Professionals Suggest?
Considering all the risks and limits of fixing Thunderbird and Office 365 manually, experts always recommend backing up your data or switching to another email program. For this, they usually suggest using the RecoveryTools Thunderbird File Converter Wizard. This tool is very easy to use and offers more than 30 saving options, making it a complete solution for Thunderbird users. The best part is that it keeps all your emails, attachments, folders, and details exactly the same after the conversion.
[*]Using wrong server details or wrong settings will stop Thunderbird from adding your Office 365 account.
[*]If you have 2-step login and don’t use an App Password, normal passwords won’t work.
[*]Sometimes, Office 365 blocks IMAP or SMTP, which stops Thunderbird from working.
[*]Firewalls, network blocks, or using an old version of Thunderbird can also cause problems.
The Manual Ways to Fix This Are:
1. Cross-check the IPv6 Settings
Sometimes Thunderbird struggles with IPv6 connections. If you face connection issues, try disabling IPv6 in Thunderbird’s advanced settings to force it to use IPv4 instead.
2. Try to Reconfigure Your Thunderbird Account
Remove the existing Office 365 account from Thunderbird and add it again from scratch. This helps fix any incorrect server or login settings and ensures OAuth2 is used properly.
3. Change the Authentication Way to OAuth2
Switch the authentication method for your account’s IMAP and SMTP settings to OAuth2. This allows Thunderbird to connect securely using Microsoft’s modern login instead of outdated basic passwords.
4. Install the Updated Thunderbird
Make sure you’re using the latest Thunderbird version — updates fix bugs and add support for modern security protocols like OAuth2, which Office 365 needs.
What Professionals Suggest?
Considering all the risks and limits of fixing Thunderbird and Office 365 manually, experts always recommend backing up your data or switching to another email program. For this, they usually suggest using the RecoveryTools Thunderbird File Converter Wizard. This tool is very easy to use and offers more than 30 saving options, making it a complete solution for Thunderbird users. The best part is that it keeps all your emails, attachments, folders, and details exactly the same after the conversion.