https://www.fsf.org/resources/webmail-systems you can find something here,
sigaint is closed but the others are viable.
I think these two are the best you can find https://posteo.de( but you have
to pay a small fee) or https://riseup.net/.
You can ask for an account on this site https://www.autistici.org/, autistici
inventati is a famous site you probably already heard of it.
More info for your privacy here: https://prism-break.org/en/.
More email providers:
Hope this is helpful