[Exim] primary_hostname

Mail servers are getting a little more aggressive about who
connects and rejecting when a rDNS doesn't match. According to
the RFC, the static ip address can be used in the HELO/EHLO
instead of the domain string, which is what I wish to do since the
"official" domain is a rather unwieldy looking string (adsl-67-116-35-
65.dsl.sntc01.pacbell.net). When specifying the ip, is the syntax
this:

    primary_hostname = 1.2.3.4
or this:
    primary_hostname = [1.2.3.4]

I read something about square brackets required in the HELO, but
it wasn't clear.

Also, is primary_hostname used for anything else besides the
default for qualifying_hostname?

Rossz