VOP seems to have problems with email messages that have a "person"<email addresss> or a person/other notes domain format.
There are 6 messages in the inbox from "bill smith"<email@example.com> and 6 messages from Joe Jones/Somewhere/US
Clicking on one of the messages and then on Bill Smith, VOP will say there are no messages and to check the spelling.
Sending a message to Bill Smith results in messages going to firstname.lastname@example.org
Adding Bill Smith to "Important People" produces the same "no messages found" error.
Additionally, if Joe Jones is a user in an adjacent domain that sends a message as Joe Jones/Somewhere/US. VOP finds the name "Joe Jones" and again, finds no messages.