I've been reading for hours on this and am still stuck.
Everything I've read indicates I need my hostname and a domain name to get a FQDN. But what about a setup where I have one hostname, using Apache, and also virtual hosts with several domain names, and I am wanting to setup a mail server for a few of the domains.
If I choose one domain name as part of the FQDN what happens to functionality of the other domains? It would seem to me that since all the domains are virtualhosts, which resolve to the same IP, that I could choose any domain name for the FQDN and it would work for all the domains... correct? Or do I just add as many FQDN entries as there are domain names?
So does a hostname of mybox with the domains example.com, as well as example.net and example.org, mean that in my /etc/hosts/ file I write
127.0.0.1 localhost.localdomain localhost
188.8.131.52 mybox.example.com mybox
184.108.40.206 mybox.example.net mybox
220.127.116.11 mybox.example.org mybox