Your admin must have enabled this feature for Gmail per the instructions in this article. If emails are not rolling up please check with your admin to ensure this setting is enabled.
Different users in your organization may need to see emails in different places. For example, a sales rep may only be concerned about emails on a specific opportunity while an account manager may be more concerned about all the emails for a customer.
When a user saves email to child records such as Contacts (child of Customer) or Opportunities (child of Customer) NetSuite will also show that same email on the parent customer record eliminating the need for users to save the email two times.
Child Records that will automatically roll emails up to parent records.
When you save an email to any of the following child records using CloudExtend Outlook, the email will AUTOMATICALLY rollup to the parent record for you - without you having to actually check it off:
Contacts | rolls up to their parent, ie customer, lead, partner, vendor
Cash Sales | rolls up to customer
Estimates | rolls up to customer
Invoices | rolls up to customer
Opportunities | rolls up to customer
Sales Orders | rolls up to customer
Purchase Orders | rolls up to vendor
Vendor Bills | rolls up to vendor
Please note : The above scenarios will only show up on the communication tab and NOT the Gmail tab.