firstname.lastname@example.org (David W. Tamkin) wrote:
> Probe messages work only if the refusing site sends you back the text, or
> sends you back your outgoing subject, or at least returns something that
> distinguishes one probe message from the others. Prodigy tells you only that
> such-and-such a user ID is not valid: no text, no Received: headers for the
> trip from your site to Prodigy, no trace of your Subject:, nothing...
Actually there is a way around this problem if you have forwarding/alias control
at a site, i.e., you can configure your local mail transfer agent (MTA) so that
many addresses all deliver to you.
Instead of (or in addition to) serializing the Subject header in each probe
message, you also serialize the From: and Errors-To: headers as follows:
Subject: List Test #001347
This is a list test message - please ignore it.
Now even the most uncooperative Prodigy-class mail agent can't help revealing
which message it's bouncing, because each one will be delivered to a unique
"userid." Even if they omit a To: header in the bounce, you can examine the
Received: headers for the delivery address your local MTA saw.
This is particularly easy to do with today's "virtual servers" that forward
email@example.com to the same address.