Mail on new MacBook Pro stuck downloading

I have a new Macbook Pro with Tahoe. I migrated successfully, but now it is stuck on downloading mail. New mail is not coming in to the Mac, but it's coming in to my iPhone and my old MacBook Pro. Downloading mail just hangs for days. Recently I deleted one of my email addresses to attempt to fix not being able to choose a signature (signature still didn't enable me to choose one after) and added that email address back into Mail. All email addresses (3) in Mail are Microsoft Exchange. Not using iCloud for Mail.