exim – What should I use for a hostname on a dedicated Linux server?

I recently came across a Debian wiki not recommending to set eximof primary hostname explicitly. From what I can gather, here is the code that chooses primary hostname.

Basically, let me have FQDN in / etc / hostname (myhostname.example.com), or just myhostname and a line / etc / hosts:

ip.add.re.ss hostname.example.com hostname

Now, what IP address? 127.0.0.1 or an external?

I imagine that the point of access FQDN localhost is correct. So, myhostname in / etc / hostnameand the following in / etc / hosts?

127.0.0.1 myhostname.example.com myhostname localhost

It looks very promising for me:

$ hostname
myhostname
$ hostname -d
exemple.com
$ hostname --fqdn
myhostname.example.com

Other than that exim would probably use myhostname.example.com for the greeting (EHLO). And this could have an impact on the fact that emails are considered spam or not. That, or I have to send a mail of myhostname.example.com, No exemple.com?

Can any one possibly break the cycle for me? Well, it's not just about exim. Are there optimal settings that would make everyone happy or most of them?