On Fri, Jan 08, 2016 at 09:37:27AM -0500, Robert Blayzor wrote:
> Is there a way/best practice to verify the forwarding address before
> accepting the message being delivered? This would allow us to reject
> it at SMTP time rather than letting thousands of messages queue up for
> delivery and then ultimately bounce.
You could try recipient verification with callouts
http://www.exim.org/exim-html-current/doc/html/spec_html/ch-access_control_lists.html#SECTaddressverification
You might get blacklisted for this though.