send a mail to 2 addresses

 
I set the "To:" field to "a@a.com, b@b.com" in Tools->Options->EMail tab.
And I use SendMail() function, but I can't send a mail to 2 addresses.
MetaTrader converts the "To:" field to '"a@a.com" <b@b.com>'.

Could you show me how to send a mail to 2 addresses?
Reason: