John Levine:
> There is a somewhat popular convention that if a domain publishes an
> MX like this:
>
> whatever.example MX 0 .
>
> it means the domain does not receive mail. There was a draft about it
> in 2005 but it's never been formally standardized and the question has
> arisen how widely imlplemented it is.
>
> I don't see anything about it in the postfix docs. Does Postfix
> do anything special with such an MX? Or if not special, does it
> fail deliveries?
For all Postfix versions, this is an invalid MX hostname. As of
Postfix 2.3 an invalid result is a permanent error like NXDOMAIN.
In other words Postfix does the right thing for "MX 0 ." but
refuses to treat it like a special case.
Wietse
