> On May 9, 2018, at 11:36 AM, Tobias Koeck <tobias.ko...@gmail.com> wrote:
>
> if I want to use several domains on my Postfix server do every domain need a
> unique PTR DNS entry to an unique IP or is it enough to setup $myhostname to
> the main domain?
1. Though IP addresses can map to multiple PTR records, this is not a good idea.
Publish exactly one primary name for each IP address via a single PTR record.
2. When handling multiple domains, it is much better to use a single MX hostname
for them all:
foo.example. IN MX 0 smtp.example.net.
bar.example. IN MX 0 smtp.example.net.
baz.example. IN MX 0 smtp.example.net.
...
Put all the indirection into the MX record, rather than use (outside the SMTP
standard) CNAMEs in the MX hostname, or define multiple hostnames with the
same
underlying IP addresses.
The myhostname setting of a Postfix MTA should ideally be a non-CNAME that maps
to
its A/AAAA records.
--
Viktor.
