IdPOP31.Host:='pop3.хостинг.ru';
IdPOP31.Port:=110;
IdPOP31.Username:='логин';
IdPOP31.Password:='пароль';
IdPOP31.Connect;
IdMessage1.Clear;
if IdPOP31.CheckMessages<1 then Break;
IdPOP31.Retrieve(1,IdMessage1);
Memo1.Clear;
Memo1.Lines:=(IdMessage1.MessageParts.Items[0] as TIdText).Body;