Hi,
My story short, maybe someone helps: all answers (up to this date) on this thread didn't work for me.
I've tried them all, multiple times.
I manage iPhones in my company, and I had several other iPhones with same email certificate and working without problems. I've changed to another iPhone and still didn't work. This issue is apple ID specific, I guess it has some bad left-overs from previous accounts.
What I did, and maybe you can, is to get another email account, with same credentials and that you know it works fine already on another iPhone. With that account, I got immediately this misfortunate "Trust" button
So, it looked like this:
- delete all email accounts, restart iPhone
- create another email account that you know it works on another iPhone with the same email certificate
- when verified, create your email account with "non-working" certificate
- It should be verified without problems, if not
- use outgoing mail server SMTP settings of previous working email for non-working (Primary off / Other SMTP settings on)
Cheers,