Mail settings unable to set certificates to Trusted anymorw

I am very frustrated with Apple having removed the ability to allow certificates for your mail server to be set to trusted. This feature was allowed in previous versions of IOS (I believe 10.4 and earlier), but then this was stopped. You are still able to set certificates to Trusted on Mac OS which is great, but on iPhone this causes huge issues! You have to delete your email account and then reset it. When this is done you lose your Sent items in mail (POP3) and if you have downloaded your server emails permanently you will also lose all of these when stores on your iPhone. This is a ridiculous issue for technology in 2021! Any helpful comments or even solutions welcome - Apple support say you have to delete mailbox and reset it - I was even told twice I would not lose any emails - this is not true!