Please modify your code to log into the logwriter like this and send us the created log as well as content of the ex.ToString():
try
{
Imap clientt = new Imap();
clientt.LogWriter = new Rebex.FileLogWriter(@"c:\temp\log.txt", Rebex.LogLevel.Debug);
clientt.Connect("imap.yandex.ru");
clientt.Login("elseeker@yandex.ru", "******");
clientt.SelectFolder("Inbox");
ImapMessageCollection fromRebex = clientt.Search
(
ImapSearchParameter.From("embarcadero.com")
);
MessageBox.Show("2");
MessageBox.Show("messages " + fromRebex.Count);
}
catch (Exception ex){ MessageBox.Show(ex.ToString()); }
Seeing the log would enable us to see what is going on and help you solve this issue.