imap issue when trying to add BT email again.

z285 wrote:

My emails stopped updating for no reason on my iPhone 13 so I deleted the account and am trying to re-add it.

However it keeps saying IMAP server mail.btinternet.com doesn’t support Password authentication. Please check account settings and try again.

How do I resolve this please? I don’t even know what password authentication is on my phone or at least how to turn it off!

Thanks in advance.

Looks like BT requires 2FA to use their account on a 3rd party app. You'll need to contact BT support to find out what authentication will work with their mail.