If you are getting the following message on your iPad or iPhone in mail:
Please try the following fixes:
FIX 1. Restart Your iPhone
If you receive an alert saying that your iPhone “cannot verify server identity”, the first thing to do is restart your iPhone. This simple step can occasionally fix a minor software glitch that could be causing this error.
To restart your iPhone, press and hold the power button until you see slide to power off appear near the top of your iPhone’s display. Use a finger to swipe the red power icon from left to right to turn off your iPhone.
Wait around a minute, then press and hold the power button again to turn it back on. You can release the button once the Apple logo appears at the center of the display on your iPhone.
FIX 2. Close The Mail App, Then Reopen It
When the mail app isn’t working properly, try closing out of the app and reopening it. This can occasionally resolve minor problems if the app’s software crashed while you were using it.
To close out of the Mail app, double-click the Home button, which will open up the App Switcher. Use a finger to swipe up on the Mail app until it no longer appears in the App Switcher.
FIX 3. Delete Your Email Account, Then Add The Email Account Again
Deleting and re-entering your email account information resets your email’s server identity certificates, which allow your email account to be verified by the Mail app. Don’t worry — deleting an email account on your iPhone will not delete your actual email account.
Here are some guides to assist: