This article describes some possible causes (with solutions) if you are unable to authenticate with VT Exchange Online using non-Microsoft clients (Mac’s Mail Client, preinstalled 3rd party mail apps on mobile phones/devices, Thunderbird, ALPINE, etc.)
We strongly recommend using the Outlook desktop application, the Outlook Web App (OWA), or the Outlook Mobile App (OMA) for connecting to VT Exchange Online. Instructions for doing this can be found at Accessing Your Virginia Tech Exchange Online Account.
It is possible that you could be experiencing an Outdated Account Profile in addition to other problems listed below. If you try a solution, and it doesn’t work, follow the instructions for Outdated Account Profile.
For example, some clients’ operating systems are too old to support Microsoft’s Modern Authentication; they have an Outdated Operating System. However, updating an operating system to support Modern Authentication doesn’t guarantee that your profile will be updated as well. It may still be configured to use the older authentication mechanism established at the time of profile creation. They have an Outdated Account Profile.
You are using an operating system version that is outdated (older than iOS 11, iPad OS 13.1, or macOS 10.15) or does not support Microsoft’s Modern Authentication which is based on OAuth 2.0.
Solution: Update your operating system to its most recent version.
Your account profile has outdated information that will not update. This cause is most likely to be seen when the university deprecates the older framework (Basic Authentication) and replaces it with the new framework (Modern Authentication). This will be a phased implementation starting on 9/15/2021 and ending on 11/15/2021.
Solution: Delete and recreate your profile.
Instructions:
Some pre-installed manufacturer 3rd party apps do not support Microsoft’s implementation of OAuth 2.0, Modern Authentication, which is required to connect to VT Exchange Online.
Solution: Switch to the Outlook Mobile (OMA) mobile app. Instructions for doing this can be found at Accessing Your Virginia Tech Exchange Online Account.
Solution: Delete and recreate your profile.
Instructions:
Outlook 2013 does not support Microsoft’s implementation of OAuth 2.0, Modern Authentication, which is required to connect to VT Exchange Online by default.
Solution: You can either update to the latest version of Outlook desktop (Recommended, Microsoft 365 Install Instructions) or ensure you have the latest service pack and edit your registry (Instructions are here: https://support.office.com/article/Enable-Modern-Authentication-for-Office-2013-on-Windows-devices-7dc1c01a-090f-4971-9677-f1b192d6c910).
Microsoft’s announcement related to deprecation of Basic Authentication
UPDATE: Exchange Online deprecating Basic Authentication - Microsoft Lifecycle | Microsoft Docs