[rt-users] User autocreation

[Phil Smith III]

We don't think we dare enable auto-user creation due to spam issues.

But the usual flow is like this:

1) User emails support at ourdomain with an issue.
2) One of us creates an RT ticket, then replies, CCing RT, putting the [ourdomain #nnn] in the Subject.
3) Occasionally a customer is well-behaved enough to do a REPLY ALL, but that fails to update RT because the user isn't in RT.

Is there an easy way (presumably a scrip) to say "Any user that's ever been on a TO or CC list gets auto-added as an unprivileged user"?