Thanks for getting back to us, @DebC-TSB.
 

We're happy to hear that the resolution shared by my colleague, @JamesAndrewM, above was able to resolve your concern regarding emailing invoices in multi-user mode. If you need additional assistance with QuickBooks Desktop (QBDT), please don't hesitate to visit the Community. We're always here to help everyone.
 

Stay safe and have a great rest of the day!