[Exim] The role of @mx_any

Hello,

    First off, I apologize if this question is trivial, or answered
somewhere else.  I did spend time looking for the answer, but didn't
find anything concrete, so here I am.

In my exim configure file I have the following lines:

domainlist local_domains = @ : lsearch:/etc/virtual/domains
domainlist relay_domains = @mx_any

A couple questions about this configuration:

1. relay_domains does not occur anywhere else in the config file, is
this a variable used within exim or can this be removed from my config file?

2. According to the documentation, @mx_any matches any domain that has
an MX record pointing to the local host. The file /etc/virtual/domains
has a list of all domains that I am the primary MX for. So can I safely
change the first line to:
domainlist local_domains = @ : @mx_any

Are these equivalent?

Thanks.

-Brett

--
Brett Humphreys
BuildLinks
Software Engineer
brett@???
919-425-0282 x114