>How safe will it be to have a server in my house for my personal email and webpage?
Install gentoo and run all webserver related services on their own user account so if they get hacked the attacker doesn't have root or other access to anything that would let him easily privilege escalate (e.g. graphics card access).

Currently i'm trying to find a secure non-root alternative to courier-imap :/

>However, I don't think somebody will make the effort to crack reasonably encrypted content.
encryption has nothing to do with this.
if you are worried about the content of your emails then you need to pgp encrypt them, but that is unrelated to running your own mail server and unrelated to the mail server's security.
reminder that all emails that aren't pgp encrypted and travel over the internet are read at least the very least by the NSA's AI.