How-to add custom macro to email Template?

1. Open an email template (Email this Issue settings / Outgoing emails / Templates / Your template / Edit)

2. Go to the "HTML Template" editor.

3. Click on the "Open raw HTML editor" and insert your Velocity code at the top of the HTML code between <!-- and -->

4. Ckick Apply and Save.

Result: If the code is okay, you can use the macro in your email template.