Save Emails is a Google Sheets add-on that is available to all users with a Google Account.  It works for Gmail and Google Workspace accounts.

Individual users and GSuite users can download the add-on from the Google Workspace Marketplace.

If you have issues installing any Gmail or Google Drive add-ons for Google Docs and Google Sheets, please try these options:

Enable Google Docs Add-ons with Drive SDK

1. Sign-in to your Google Admin console.
2. Go to Apps > G Suite > Drive > Data Access and check the option “Allow users to install Google Docs add-ons from the add-ons store.” Save the changes.
3. Check the option “Allow users to access Google Drive with the Drive SDK API.”
4. Click Apps > G Suite > Drive > Data Access and check “Allow users to install Google Drive apps.”
5. Save Changes.

Enable Gmail and Google Drive in Google Workspace

1. Go to Apps > G Suite > Drive and Docs and make sure the Google Drive service is enabled for your account. Choose “On for everyone” to turn on Drive for all users in the organization.
2. From the Admin console dashboard, go to Apps > G Suite > Gmail and turn on the service if it is OFF for the user.