ExtendSync will copy your Gmail to the desired Netsuite records. In some cases, users have reported that the email appears with all of the HTML markup as opposed to just the HTML formatted email.
Our engineers were able to identify an existing issue on NetSuite defect: 532370.
Resolution
The indicated workaround for this is the following:
Step 1: Navigate to Home > Set Preferences > User Profile.
Step 2: Un-check the Add Signature to Messages checkbox or Clear Browser Cache.
or
NetSuite has also advised the following has worked for their users:
Step 1: Open an existing Email in NetSuite (not Gmail) using Chrome (email opens in a pop-out window).
Step 2: Copy the URL of this window and put it into a new Chrome tab.
Step 3: Press F12 for the Chrome Developer Tools, and then right-click on the browser Reload button.
A drop-down menu appears.
Select Empty Cache & Hard Reload.
Step 4: Close the unnecessary tabs and view your email again.