2. Login to NetSuite and navigate to Customization > Scripting > Scripts > New > User Event.
3. Give the script a name.
4. On the 'Script File' field, upload the JS file created in step number 1.
5. Indicate the function name ''setRecEmailAddress" on the "Before Load Function" field.
6. Hit on Save.
7. Click on 'Deploy Script'.
8. Select 'Message' on 'Applies To' field.
9. Set the 'Status' to 'Released' and check on 'All Roles' checkbox.
Note: This is the alternate solution to Enhancement 258510: Project > Email > New Email Message pop up > auto-populate the Email Address by the email of the Contact on the Project.