Insufficient storage for email despite available space on iPhone

Hey! I am currently in college and went through rush. I know how to set up a FSID and Myphi mu account. However they weren’t able to email because it says the email was bounced and I didn’t have storage.i was told to delete as much stuff as I could. There are no emails in my email and went I checked my storage it says 82 gb used out of 128gb so I have enough storage.

[Re-Titled by Moderator]

Original Title: Storage