Recently, I faced up with strange behaviour of ResolveName method of ExchangeService class. This method should finds and resolves contacts in a specified user’s Contacts folder and the Global Address List (GAL).

Method is called in the following way:

    var emailAddress = @"user@example.com";
    var resolutions = service.ResolveName(emailAddress);
    if (resolutions != null && resolutions.Count > 0)
        return resolutions[0].Mailbox;
    return null;

where service is the [correctly] initiated variable of type ExchangeService class.

In the following instances ResolveName method returns the empty list:
1. Email address is incorrect;
2. If user‘s account is hidden from Exchange address list.
But one of the customers has Exchange installation and/or ActiveDirectory settings such that ResolveName method returns the empty list for correct non-hidden mail address. Unfortunately, I didn’t find any reasons of such behaviour.

1. All used IP-addresses, names of servers, workstations, domains, are fictional and are used exclusively as a demonstration only.
2. Information is provided «AS IS».