Apple iOS Mail does NOT support email encryption using non-Exchange accounts

Despite what Apple claims in this article, iOS Mail does not support encryption using non-Exchange accounts. It will sign messages fine, but try to send one to yourself and it it 'cannot locate identitiy' of recipient. Apple support has told me to contact my email provider. However I have set up encryption in Thunderbird on my Windows PC, using the same email account, and encryption works fine. An encrypted email to myself sent via Thunderbird decrypts just fine on iOS mail. But replying encrypted fails.

This issue is posted in numerous places on Apple and it is very frustrating that they are not addressing it. It is particularly frustrating when they leave up incorrect articles like this one.

I have spent hours trying to get encrypted email to work. It is becoming essential in this era and it should not be this hard. We need more support from our tech companies.