iOS 11.3.1 Mail app doesn't shown new mail until the iPhone is rebooted - any cure? I have an iPhone 6s running iOS 11.3.1.  The Mail app is able to download and display e-mail from my GMail account.  However, e-mail to my account at register.com is frequently not displayed until I have powered off the phone and powered it back on.  The webmail service at register.com shows that the e-mails have been received, and the iPhone actually shows a little message saying "Downloading 5 of 5" or whatever, but the e-mails never appear.

We all know that 11.3.1 is something of a failed release, but has anyone else experienced this problem and found a solution that doesn't involve turning the phone off and on to receive new mail?
A couple of things to try


Delete the Account from your phone and re add it.
Go into Settings > General > Reset and reset the network settings


You will lose the WiFi networks you have already been on and authenticated to but all you have to do is re-connect and re-authenticate.


Failing the above I would back up the phone (password protect the backup so you don't lose your saved passwords.) Wipe it (Settings > General > Reset > Erase all content and settings) and then restore from the backup you just made.