Solved the problem. I read IMAP protocol documentation more closely and I saw how sending TIMAPSend (synapse). Each instruction must be completed by CRLF string, example:
const
CR = #$0d;
LF = #$0a;
CRLF = CR + LF;
begin
LTCPComponent1.SendMessage('A001 LOGIN ' + editLogin.Text + ' ' + editPass.Text + ' ' + CRLF);
end;
LNet works great