On 11th August emails no longer received. There may have been an update about that day?
Message in email settings is: Couldn't verify account. A security connection error has occurred.
In settings changed 'SSL' to 'SSL (Accept all certificates)' and emails now received. But I should not have to modify that setting from the default, as it makes emails less secure.
I use Firebird for desktop and all emails received there OK.
Checked my email settings for my domain: I have self-signed certificates and they are current.
There was another update to my phone on 15th August, but that did not fix this problem.
A suggest fix is to delete account and recreate it. As a test I first created another email account at my domain and set that up on the phone and the same problem occurs. So Im not sure deletion and recreation would work.