some keys, like 25FC1614B8F87B52FF2F99B962AF4031C82E0039, have a user ID that has no e-mail address. If the user indicates that they intend to certify that user ID, its certification should be attached to any other certification that *can* be sent -- so the certifications are sent in tandem. So for example, if an OpenPGP certificate looks like: uid 0: Alice Jones uid 1: Alice Jones <alice@example.net> uid 2: Alice Jones (CEO) <boss@example.biz> then the e-mail that goes to `alice@example.net` should contain the certification for User IDs 0 and 1, and the e-mail that goes to `boss@example.biz` should contain the certification for User IDs 0 and 2. That way, if the recipient gets any of the e-mails, they can see a certification over the user ID that has no e-mail address. What monkeysign currently does in the above scenario is to try to send the certification of User ID 0 to "Alice Jones", which is typically treated as a bogus e-mail address and gets bounced. The behavior i'm proposing is how caff handles this kind of User ID, fwiw.