The working example from my project:
function SendMail(server, port, mailfrom, user, pwd: string; ssl: boolean; mailto: string; body: TStringList): boolean;
var
m: TMimemess;
p: TMimepart;
begin
Result:=False;
m:=TMimemess.create;
try
p := m.AddPartMultipart('mixed', nil);
m.AddPartHTML(body, p);
m.header.from := MailFrom;
m.header.tolist.add(MailTo);
m.header.subject:='Message from my system';
m.EncodeMessage;
SendToRaw(mailfrom, mailto, server+':'+port, m.lines, user, pwd);
finally
m.free;
end;