How to send digitally signed emails using iOS Mail (iPhone/iPad) ?

10 Mar ‘23

When you wish to send an S/MIME based encrypted email using iOS Mail, your iPhone or iPad needs to be aware of the S/MIME certificate of the recipients, and you must have a valid S/MIME certificate installed in iOS.

You can either manually install an S/MIME certificate on your iOS device, or have it installed by an MDM solution such as Intune or Mobile Iron.

To manually configure your installed S/MIME certificate for iOS Mail, go to: Settings -> Mail -> Accounts -> <Select your account> -> select the account again -> Advanced Settings -> Sign -> <select the available certificate> -> back  -> Account -> Done

Source: https://support.apple.com/en-us/HT202345