This stops unauthenticated users from sending unauthorized emails.
Example:
`swaks -t matteo@mail.saloniamatteo.top --header "Subject: Unauthorized Email" --body "This email should not go through." --server mail.saloniamatteo.top`
Before this patch, any user could run the command above, without any authentication, and the server would gladly accept the incoming mail.
Now, the email is rejected, and the email server only allows authenticated users.
Ubuntu can't run multiple lines without a special character, thus making the script malfunction, putting the commands on the same line solves the problem and the script can be used on Ubuntu 20.04
According to the wiki (https://wiki.dovecot.org/SSL/DovecotConfiguration):
"From version 2.3, you must specify path to DH parameters file using:
ssl_dh=</path/to/dh.pem"
This actually threw an error something along the lines of: "imap-login: Error: Failed to initialize SSL"
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