Why cant I connect to an email server

[toneeeee]

I have had an issue with me email on my Oneplus3 phone. A couple of days ago it just stopped downloading messages over IMAP.

It turns out the certificate expired on the mail server and was changed. When i look in the email account settings and try to validate the email server with the new certificate it keeps picking up the old certificate from some sort of internal cache and saying its invalid.

I have tried to clear the credentials in the security option, I have deleted the account and tried to add it again, but the same issue.

How do I clear the certificate and force the email client to pick up the new certificate?

Thanks for any advice!

 

[N4Newbie]

Try the various "credentials" options under Settings -> Security.

 

[toneeeee]

I have tried all of them, but still cant seem to delete the cached cert