Keine Ahnung warum Canon diese Funktion nicht in das Webinterface integriert hat, aber so stellt man den SMTP Port um.

In meinem Fall benötige Port 587 (Office 365)

Canon Advance Series - Change SMTP port to 587  

How to enter Service Mode 1 and 2 on Canon imageRUNNER C5560i / C5550i /C5540i / C5535i Printers

How to enter the Service Mode on a Canon imageRUNNER ADVANCE series
1 Press and release the “User Mode” or ” * ” (asterisk) key on your Canon's keypad.
2 Press and hold the “2” and “8” keys simultaneously.
3 Press and release “User Mode” to enter the service mode.

Changing a Canon imageRunner Advance email port setting to work with Gmail (Port 465 SSL)