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Email - de-duplication in Gmail, G Suite for Domains, and xMail

This article explains the concept of de-duplication within email systems. Under certain circumstances in Gmail, G Suite for Domains (formerly known as Google Apps), and Exchange, mail is de-duplicated resulting in recipients only receiving one copy of a message sent to the recipient multiple times, or recipients not receiving messages sent via to their Google accounts.

Gmail and G Suite for Domains

If a user forwards their mail to a or G Suite for Domains and then tries to send a message from Gmail/G Suite to their address, they will never receive it in their Gmail/G Suite inbox. Google has message de-duplication as documented here:

This also happens if a user sends to address from Gmail/G Suite for Domains. If the user is a subscriber to the address, she will never receive the message as distributed by the server.

Example:, is a subscriber to Bob sends a message to Bob will never see the distributed message from in the Gmail inbox.


Bob,, forwards their mail to their private Gmail account, Bob sends a message from Gmail to their account,, to test if mail forwarding works. Bob will never see the message in the Gmail inbox.


If an xMail user is a subscriber of two address and a single message is sent to both lists, the xMail user will only receive one copy of the distributed message.


Bob, an xMail user, is a subscriber for and Sally sends a message To: and Cc: Bob will receive this message once, and it may appear to come from either or

Keywords:mail, de-dupe, xmail,, GoogleApps, google, apps, gsuite   Doc ID:21893
Owner:Paul B.Group:University of Chicago
Created:2011-12-21 11:42 CDTUpdated:2017-04-06 13:24 CDT
Sites:University of Chicago, University of Chicago - Sandbox
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