Issue
When you try to log in to Apple's Mail app which has been set up according to the instructions, the app continues to ask for a username and password. However, you are able to log in to https://office365.bowdoin.edu correctly.
Cause
As of October 16, 2019, all Bowdoin community members using Office 365 will have a new single sign-on experience. This includes Outlook Online, Word Online, Excel Online, OneNote, and OneDrive.
Resolution
In order to continue to use Apple's Mail app there are two things that you may need to do.
Remove and then re-add your Bowdoin mail account
In order for Apple's Mail app to recognize the new single sign-on experience, you may need to remove and then re-add your Bowdoin account to Mail. Follow the instructions titled "Reconfigure Apple's Mail app for Office 365" listed under the "Related Articles" section for more information.
Upgrade your operating system
All versions of MacOS before 10.14 Mojave do not support what is referred to as "modern authentication". When trying to access older versions of Mail, you will be continually asked to log in without success.
In order to continue to use Apple's Mail app, you will need to update MacOS to the latest version, 10.14 Mojave, which is freely available in the Mac App store if you use a personal computer, or is available as an upgrade in Self Service if you use a Bowdoin-issued computer.
NOTE: You must then remove and then re-add your Bowdoin account in order to have Apple's Mail app to recognize the new single sign-on experience. Follow the instructions titled "Reconfigure Apple's Mail app for Office 365" listed under the Related Articles section for more information.