Your invoice email message is a template that will appear when you send the invoice via email. These can be edited and personalised to each job by entering tags, like the job date, invoice total, customer name, location, etc. You can customise this message through your system settings. From the 'Invoicing' section, click into 'Invoice email message'.
From this page, you can use the dialogue box to craft your message. Click 'Use tagging' to open a sidebar containing all the available tags. These are used to personalise these emails to each customer by invoice total, address, name, number, and any other pertinent information. Start typing your message and click on the relevant tag when you want to enter customer data such as work address. Once you are happy with your email click 'Close tagging' and then hit 'Save'. This message can be edited further if the need arises later.