Email Logged Using Salesforce Outlook Integration or Gmail Integration Appears Multiple Times on Salesforce Records

Root Cause 1: Shared Activities Feature Is Not Enabled

When the Shared Activities feature (Allow Users to Relate Multiple Contacts to Tasks and Events) is not enabled in an organization, Salesforce creates a separate email task record for each Contact to which the email is logged. This results in duplicate entries appearing in Activity History on the Account and Opportunity.
This behavior occurs when the following settings are in place under Setup > Activities > Activity Settings:

• Roll up activities to a contact's primary account is ENABLED
• Allow Users to Relate Multiple Contacts to Tasks and Events is DISABLED

When Shared Activities is enabled, an event or task can be related to up to 50 Contacts, creating a single email record in Salesforce instead of multiple records for each Contact.
Before enabling Shared Activities, review the considerations for your organization in the Additional Resources section.

Root Cause 2: Custom Code (Trigger, Process Builder, or Flow) on the Task Object

If Shared Activities is enabled but duplicate emails still appear, the issue may be caused by custom automation (Triggers, Process Builder, Flows, etc.) on the Task object that prevents Task deletion.
When an email is logged to both a WhoId (Contact) and a WhatId (Account, Opportunity, Order, Contract, Campaign, or Custom Object), Salesforce standard logic inserts two or more Task records and then deletes one — keeping only a single Task that displays both the WhoId and WhatId. If a custom trigger or automation prevents this deletion, duplicate Task records remain.

How to Verify Duplicate Tasks

To confirm whether duplicate Tasks are being created and retained, query the Task object using Workbench or Data Loader. Filter by the email subject and look for records where IsDeleted equals true with blank WhatId and WhoId values. A deleted record with blank IDs confirms that Salesforce's standard deduplication logic ran but a second copy was retained due to custom code.
Example query filter: Subject LIKE '%Email: Your Email Subject%' — all task records created from an EmailMessage have a Subject prefixed with "Email:" and a TaskSubtype of "Email". Modify any custom automation to exclude tasks with these field values to prevent unexpected behavior.