One of my friends told me yesterday that after updating to iOS 10 the email accounts used in the Mail app have stopped receiving new emails. It displays an error message saying “Your password is incorrect.”
Even re-entering the password doesn't fix the issue, or for that matter stops the error message from appearing again. Have you also come across this problem on your iPhone post updating to the latest iOS ecosystem? Here are some quick tips to troubleshoot an issue.
Fix Mail App Not Working Issue in iOS 10 on iPhone and iPad
Solution #1: Force Reboot Your iOS Device
A few minor bugs like freezing of touch screen could be fixed by force rebooting the device. So, try to give this trick a luck.
Simply press and hold the Home and sleep/wake buttons at once on your iPhone or iPad until Apple logo appears on the screen. (To force reboot iPhone 7 and 7 Plus, check out this post.)
Solutions 2: Change the Passwords
Try changing the passwords of your email account. To do so, simply enter the wrong password while signing into your account, then select forget password and reset it as usual.
Solution #3: Remove the Affected Email Accounts and Re-add them
Step #1. Open Settings app on your device → Tap on Mail.
Step #2. Tap on Accounts.
Step #3. Next, you have to tap on your email account.
Step #4. Now, tap on Delete Account.
Step #5. Tap on Delete from My iPhone to confirm.
Step #6. Now, re-add your account. (Tap on Add Account, select the service, sign in with your ID and passwords.)
Solution #4: Reset All Settings
Resetting your device to factory settings can help you resolve the issue.
Step #1. Open Settings app → General → Reset.
Step #2. Tap on Reset All Settings and confirm.
Solution #5: Restore Your iOS Device as New Using iTunes
If all the above-mentioned solutions are not able to fix the issue, then restore your iPhone as new. Make sure to backup your iOS device before restoring it.
Hopefully, these tips are able to help you resolve the problem.