Well I didn’t want google to read my mails

Sadly, it only works if no one in the recipients of the mail is on gmail (or if everyone use pgp, which I would tend to think is even more rare).

I host my own mailserver as well, and I would add as benefits:

• creating as many email address as you want easily, possibly regexp based address (awesome to give every site a different address and know where the spam comes from, without using the well known schema username+something@host). That also makes routing/filtering mails way more easy, you just have to match the recipient address.
• delivering mails to software, to put email at the center of interapps messaging (basically, that means that postfix pass a matching email to the executable of your choice on your system instead of storing it in your mailbox)
• advanced rules for handling emails. When I want to block a spammer that managed to get my real email, I use regexps to match their mails and reject it with a “REJECT 5.1.1 Recipient address rejected: User unknown in local recipient table” error, imitating the error for unknown users, which often triggers a mail system to remove your address from their database
• easily configure apps to send me email. When I write an application that will send emails to me and only me, I configure it to use my smtp on port 25 without authentication instead of the usual smtps configuration they expect. It connects to it and asks to send a mail to me, which is accepted since I’m a local user. It makes everything way easier (try to do that with gmail and get your IP banned)
• easy backups. Both of the mail system (I backup the whole sdcard of the pi) and of the emails. Never lose an email again.