names in contact groups disappear.

[Guest]

I have groups of 50 addresses that I regularly send e-mails to. Today, all
the names in the groups have disappeared except those few that are also in
the main address book.

 

[Russ Valentine [MVP-Outlook]]

The term group has no meaning in Outlook's context. Define what you mean by
it. Outlook does not use an address book. Define what you mean by it. Might
as well include the other information we would need like Outlook version and
information store.