I believe this is actually part of a larger issue - that MYOBs Email sending capabilities simply don't include many features that Outlook offers. This is why i made a suggestion to add a setting to get MYOB to compose the Email in Outlook, but NOT send it (at the moment it composes the email in Outlook and sends it automatically with no way to stop it or change it) - this will allow the user to modify the contents, add attachments, etc.
Its great to hear that you have voted for @ActionCranes's idea.
In terms of the idea that you have lodged previously. At this stage of that idea we are encouraging clients to vote and comment (if required) for that particular idea. We don't have a time frame for when that (or this) particular idea will be placed into development and implemented into the program.
We require this function too. I'm having to send employees site Time Sheets in a seperate email, whereas I use to save the payslip and combine it with the time sheet. I would love to be able to just attach the time sheet so they receive it in the same email as their payslip.