Cannot verify server identity” Issue!?
I am constantly getting this pop up that cannot verify server identity
You may have a subscribed Calendar or a CardDAV account for Contacts or Calendars.
What happens when you click the "Details" on the error popup message (See the Pic below)
Best would be to Delete and Add the email account that is creating the issue.
You may also try changing SSL settings
Settings > Password & Accounts > [Select the Mail account} > [Tape on Account with the email ID} > Advanced > SSL Settings > [Disable]
Click <Account (in Blue)
Click on DONE (in Blue) when exiting in the previous screen