In case you are handling different matters for a single client and would like to email invoices for work done on each matter, you don't need to separately send each invoice.
To bulk email invoices at once:
1. Head over to the Invoices tab
2. Check the Invoice Number box to bulk select all invoices
3. Click the Send by Email button
4. Edit the bulk email and click Send
Note: You can also bulk delete, mark as sent, download, and bulk print. Execute any of those alternative actions by selecting the applicable option when you check the Invoice Number checkbox.