using (Imap client = new Imap())
{
    client.Connect(_server);
    client.Login(_user, _password);
    client.SelectInbox();
 
    client.GetAll()
        .ConvertAll(uid => client.GetHeadersByUID(uid))
        .ConvertAll(eml => new MailBuilder().CreateFromEml(eml).Subject)
        .ForEach(Console.WriteLine);