@rongxchen As suggested earlier, have configured the email events to understand whether the email got delivered when you send the email to your college address?
You can also troubleshoot by enable diagnostics logging for your Acs resource and query the ACSEmailStatusUpdateOperational logs (provides message and recipient level delivery status updates related to the Email service send mail requests) to check the status of the message.
Refer to these documentations for more information about how to enable diagnostic logging and also about different supported email logs in ACS
Note : MessageID will be the correlationId in this table.
If your message delievery status was showing as OutForDevlivery and you have checked all the folder and you did'nt receive email then email might in queued state.
If you still run into the issue, I would suggest you raise a support ticket for further investigations.