If you are aware that the message is not arriving in your clients' email inbox for any reason, this might be due to their spam settings or corporate firewall.
We send all the messages out via white-label protected email servers so we limit the risk of this happening. However, if the message is still not arriving you can check that the email address is right by viewing this in the Invoice Summary screen via the Invoice menu.
If you have entered the email address incorrectly, click the EDIT button and correct the email address for your client before saving.
If the messages are still not arriving successfully, please raise a Support Ticket.