The TLS certs were reprovisioned on Dec 8 2020 at 3:44 AM.
I was able to make my desktop mail app (MailMate) accept the new certificates. But the phone app cannot send mail and has not been able to since Dec 8 2020. has anyone else encountered this issue with an iOS mail app and been able to resolve it?
When I evaluated Spark it looked good but I didn’t choose it as they process your email on their servers and the privacy agreement was obscure. Maybe a concern for the OP as it was for me.