Email1EntryId is not valid in this case. Passing it into
NameSpace.GetRecipientFromID() throws an exception ("Additional
information: Could not open the item. Try again.").

A visual inspection of Email1EntryId reveals that it's not a binary
string consisting of characters [0...9, A...F], but rather it just
looks like it accessed part of the memory that stores the X500
address. The invalid value is "^\0rey Buda (ABC SS&S)
".

I inspected this contact in MFC MAPI, and the property 0x804300E1
seems to contain the value I'm looking for,
", but I'm afraid to use that unnamed
property that I've never heard of before.

Any other ideas?

Thanks,
Jeff