If you have upgraded your iPhone or iPad to iOS 11 you may encounter issues accessing your McGill email. That's because the Mail app on newly released iOS 11 is currently not compatible with Outlook.com (email on Office 365). If you are still using iOS 9 or iOS 10, you are not affected.
"Tech giant Apple and the FBI appeared headed for a deepening confrontation Wednesday after the company’s chief pledged to fight federal demands to help mine data from an iPhone used by one of the shooters in December’s terrorist attacks in San Bernardino." (The Washington Post)
For devices using iOS 6.1, Apple suggests this software update: http://support.apple.com/kb/DL1639, now available on the Apple site for those who wish to use it.
Original announcement, February 12:
A known issue between Exchange 2010 server and devices using iOS 6.1 can cause performance issues affecting both McGill’s Exchange servers and individual iPads and iPhones using iOS 6.1.