How to control Received: from in outgoing emails

[VA1DER]

My installations of Roundcube are revealing details of my configuration that I don't want them to reveal.  Specifically, Roundcube is sending the HTTP_HOST string as the local ID when connecting to SMTP and I don't want it to.  The hostname a user connects to shouldn't be used in the outgoing SMTP's Received: from header, as in some cases those are .onion addresses I don't want to be public.

I'm sure this is a FAQ, so I apologize in advance.

[VA1DER]

I answered my own question.  If anyone else is unsure, it's the

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$config['smtp_helo_host'] setting.

Unfortunately it doesn't appear to support any of the standard expansions.  I would love if it could support %s or %h (a la imap_host / smtp_host).  Consider this my vote for that functionality.