You send a message from your @engineering.ucsb.edu from the GMail app on your phone, and a day later you get a bounce message saying it couldn't be delivered.
You may have your personal GMail Account on the GMail App and your Personal GMail has a Send As address for @engineer.ucsb.edu account configured on it with the old mail server configuration.
There are two ways to deal with this issue.
Remove the Send As account on the personal account
Update the Send As Account on the personal account
At the current time, these are the two easiest solutions to enact with the third of removing the Personal Account, which may not be a great option on personally owned devices.