Well, regarding receiving, I believe you must open Outlook. I know of no way to set Outlook to automatically open when you have email waiting to be received. Same for sending if you're creating a new message in Outlook.
Regarding the possibility of Outlook automatically opening and sending email emanating from MYOB, I don't know the answer but I think it would depend on whether MYOB developers can implement that kind of interaction between MYOB and Outlook. And, even if there's a way to have Outlook automatically send multiple messages emanating from MYOB, I would guess this might depend on a setting in Outlook. I'm looking at Outlook 2003 here. If you open Tools, Options, and select the Mail Setup tab, is the box for "Send immediately when connected" checked?
You might also post your question at
http://myobforum.infopop.cc/eve