If your mailbox is in Office365, you access the Mail app from Outlook.Office.com, from the Office365 portal at: office365.bowdoin.edu or from Bowdoin's Login Portal at https://login.bowdoin.edu.
If you try to log in to webmail.bowdoin.edu you will see a page that says "Something Went Wrong. We could not find a mailbox for this user." the first time after your mailbox is moved.
To resolve this error, browse to one of the options listed above to access your email.