For #myhostname, I should uncomment and put my hostname, i.e. the name I gave my VPS, right?
Or does it just go myhostname = mydomain.net, in other words don't edit the phrase 'myhostname' except to uncomment?
And for #myhostname = virtual.domian.tld is that to put a subdomain?
Should I add a listing for all including with and without www?
The myhostname should be set to the FQDN of your mail server. For example, if your server's hostname is "mail" and your domain is "example.com", your FQDN is "mail.example.com". The directive would look like this:
myhostname = mail.example.com
On a Linux system, you can get your FQDN using the hostname command:
hostname --fqdn
This should match the PTR record for the primary IP on the machine.
See the Postfix documentation for myhostname.
For accepting mail for subdomains which are not the server's hostname, you can use the mydestination directive:
mydestination = mail.example.com, example.com, www.example.com
