There is a known issue with attempting to email directly from AccountEdge to Mac Mail on the latest Mac OS X (El Capitan or later). The PDF of the invoice or purchase, etc. will not be attached to the email when sending directly from AccountEdge. This only occurs in Mail and does not occur when sending emails through Outlook.
Update AccountEdge to fix this issue
The following AccountEdge versions eliminate this issue:
AccountEdge Pro/Network Edition v15 (and newer)
AccountEdge Basic v4 (and newer)
If you're using an earlier AccountEdge version and have a current support subscription, you're entitled to an update. Check for updates by going to the AccountEdge menu and choosing Check for updates.