schleuder only associates keys with the e-mail address on their primary (or first?) user ID (maybe *no* e-mail address!)
When i run
schleuder-cli keys list firstname.lastname@example.org it shows fingerprints and e-mail addresses for each loaded certificate.
If a certificate has multiple e-mail addresses associated with it, only the e-mail address from the first User ID (probably the primary?) is associated.
This is particularly problematic for certificates which have a primary User ID that has no e-mail address in it, like 25FC1614B8F87B52FF2F99B962AF4031C82E0039, because it runs into a similar issue as #395 (moved) -- the key appears to become associated with no e-mail address, despite the fact that some User IDs do have e-mail addresses in them.
Note that OpenPGP certificates can get updated over time (maybe just from a keyserver refresh), and each update can potentially change the e-mail address associated with the key (e.g. by switching the primary flag).
Of course, it would also be pretty weird for schleuder to just take the OpenPGP certificate entirely at its word -- anyone can add any e-mail address to their own certificate, and it would be very strange if such an update would take over some other e-mail address, so i'm not sure how to resolve this.
But at the very least, someone with a key like 25FC1614B8F87B52FF2F99B962AF4031C82E0039 ought to be able to subscribe to a schleuder mailing list and have their key correctly associated with one of the e-mail addresses that they have listed, as opposed to the empty string.
Perhaps the right solution is to explicitly bind an OpenPGP key to an e-mail address subscribed to a list within schleuder (maybe also requiring that the e-mail address in question is in some UID), but not arbitrarily accepting any e-mail address that happens to show up in the UID.