action.subscribe.gid email is not subscribing the contact

[ArthurC]

{action.subscribe.gid} generates an email to bounces@mysite.com which is supposed to tell CiviCRM to subscribe the contact with this email address to the group matching the group id (gid).

When I "Fetch Bounces" and bring the email into CiviCRM, it doesn't appear to do anything. It doesn't appear to do anything wrong either - that is, I don't see any errors. It certainly does not add the contact to the desired group which is what it is supposed to do.

The VERP string appended to the email address looks like this: bounces+s.18.0.0000000000000000@mysite.com

All those zeros after s.18 suggest that the token is not packing some important information in there.  But in token.php there's a comment for the subscribe token that says, "we add the 0.0000000000000000 part to make this match the other email patterns". That means that the VERP address is probably correct.

In that case, the code that's supposed to process the subscription is going to get the contact id from the email address of the incoming email. That all happens in subscribe.php.

Other action tokens, to unsubscribe, for example, use VERP addresses like "bounces+u.18.2011.f34d5de790c50a54@mysite.com"

action: s=subscribe (can also be "u" for unsubscribe, "e" resubscribe, "o" opt out, and other things)
gid: 18
another id: 2011=a sequence number?
hash: f34d5de790c50a54

It's likely that I've missed a critical step, but either way - whether it's me or CiviCRM, I'm stuck, and need help to nudge this through to success.
 
Thanks.