My most recent ISP does CGNAT. They don’t hide it, it’s mentioned in their support pages. A quick email is all it takes to switch you over to an open address though.
Anyway I’ve got a $5/mo server with akami that looks after my email and it’s associated domain.
It took about three hours of following a guide to set up DMARC and etc etc and it works unobtrusively, and is about ten times faster than my old ISP IMAP account that I had for about twenty years.
It was one of LinuxBabe’s guides - this one:
https://www.linuxbabe.com/mail-server/setup-basic-postfix-mail-sever-ubuntu
There is a more recent one that uses a shell script to install all the bits and pieces but I prefer to do it myself so I’ve got at least some idea of how all the pieces work.