Using subject line for reply-by-email identifier

[precessor (Dave Higgins)]

I just set up the reply-by-email function as described here:

Set up reply by email with POP3 polling

So you’d like to set up reply via email support for your Discourse forum. Reply via email is pre-configured and enabled by default on all discourse.org hosted sites. The guide below only applies to those self-hosting. Good news! Unlike outgoing email, which is completely unsuitable for typical consumer mail services like GMail, Outlook, Yahoo Mail, etc, incoming reply via-email tends to be extremely low volume. Unless you have a truly massive forum with a zillion people replying to no…

It’s working great!

For appearances, I prefer to have the reply domain at my domain rather than Gmail.com, so I thought about setting up a DNS email forwarder. I hoped that the sub address (address tag) would be preserved.I would continue to POP3 from Gmail, I don’t mind that.
However, this does not seem to be possible:
dns - Email forwarding preserving subaddress - Webmasters Stack Exchange

But a workaround remains, as described in that post: put the string identifier in the subject line as well (and look for it there as well). This would prevent Discourse customers needing to set up their own email server, which is my remaining option (I’m using a DigitalOcean droplet).

May I therefore suggest this feature: put the string identifier if a reply-by-email in the subject line as well as the address tag, and check for it there too.