FQDN

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FQDN

Me
It is said that a FQDN must be used to set up Postfix.  However, it then says that one may use the myhostname parameter.

I wish to use one Postfix server to handle mail for various domains, each with a unique and assigned IP address.  One domain does not see the other, and outgoing mail should only have the appropriate domain name in its header (not that of the server).

What should be the FQDN of the server?  Hostname -f returns centos7.is.cc in my case.  (It has an assigned IP address for the sake of remote access.)

Thank you.

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Re: FQDN

Wietse Venema
Me:
> It is said that a FQDN must be used to set up Postfix.? However, it then
> says that one may use the myhostname parameter.

To help with this, Postfix will automatically append $mydomain
to an unqualified myhostname. That is sufficient for local-only
email, and for sending/receiving all email through a local ISP.

If you want to use the Postfix server to communicate directly with
remote mail servers, then the Postfix SMTP client's smtp_helo_name
setting (default: $myhostname) should match the server's IP address.
The Postfix SMTP server always uses $myhostname.

> I wish to use one Postfix server to handle mail for various domains,
> each with a unique and assigned IP address.? One domain does not
> see the other, and outgoing mail should only have the appropriate
> domain name in its header (not that of the server).

Postfix supports different server personalities with different
headers etc. for different domains, but that requires using multiple
Postfix instances: http://wwww.postfix.org/MULTI_INSTANCE_README.html.

> What should be the FQDN of the server?? Hostname -f returns
> centos7.is.cc in my case.? (It has an assigned IP address for the
> sake of remote access.)

% host centos7.is.cc
Host centos7.is.cc not found: 3(NXDOMAIN)

Postfix sends $myhostname in the client and server SMTP handshake,
so these should resolve to the IP address. The further you err from
basic SMTP protocol hygiene, the more likely your server will be
treated as a spam source.

        Wietse