[Mimedefang] Accessing the source/destination port #'s at filter_relay

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> Only question is: should we also pass the ports and the local address to
> filter_helo()?

I can't speak for all MTAs, but for sendmail, aren't these available as environment variables?  {if_addr} (the local address) is supplied by default, and the port values can be added to the supplied macros....