Dynamic reply-to on email notification

Not applicable

We have a business rule that sends email to a group of people, and we'd like to set 'reply-to' to the address of whoever triggered the business rule that sent the message.

Apparently, service-now only allows that filed to be hard-coded. I've tested setting this to an email address (works), to the table field with the user's address (u_reply_to - doesn't work), and to the table field using ${u_reply_to} (didn't work either). Any ideas?