documentation changes

Literally added one letter

Technically Postfix is responsible for sending *and* receiving mail between *your server and other SMTP servers* (Mail Transfer Agents). Dovecot is only so you can view your mail in email clients on your computer instead of server, which is not really *receiving*. You can have a perfectly functional email system with no IMAP/POP server at all, you'd just have to read your email over SSH or whatever

Typos + other tiny corrections, is it "honestly have" or "honestly don't have" preference towards vultr? Tried to guess...