It is possible to link two QuickFile accounts so that a sales invoice raised in one account is pushed directly into the recipients account as a purchase invoice.
Have a read here:
How to link two Quick File accounts
As for the missing email, this can happen when one server (ours) is sending email but making it appear from another email address. Have a look here for more information on improving email reliability.
Improving email reliability with your own SMTP server or an SPF record