They are using Mailcow, so no, your emails are not encrypted.

In general, unless you're using PGP, email is not reasonable to assume that it's encrypted ever. I use Protonmail, and I still don't trust it at all.

Storage is 1GB by default (you can ask for more when you reach that limit), and emails are sorta encrypted. I find it weird that emails are ‘encrypted’ with a key pair that are on the same email server. I’m going to attempt to find a way to make emails encrypted with your own key/pass combination.