What’s changing

We are launching some changes to how Gmail threads messages when you have conversation view turned on. Previously, Gmail would thread together messages when either of the two conditions below are true:

  1. A message is sent in reply to another
  2. A message has:
    1. The same sender or recipients,
    2. The same subject,
    3. And is sent within one week of an earlier message in the thread.

With this change, we’re adding the requirement that an incoming message’s Reference header, if present, must reference IDs of previous messages in order to thread (see image below for example). This means that if you receive two emails with the same subject from the same sender, these emails will not be threaded together unless one explicitly references the other.

Who’s impacted

End users

Why you’d use it

This change helps to make sure that messages are only threaded when there is a definite relationship between them.

How to get started

  • Admins: No action required.
  • End users: No action required. You’ll see these changes roll out on Gmail on the web and on mobile apps.

Additional details

If you are managing a system that sends email notifications to users and want your emails to be threaded in Gmail conversation view, then you have to ensure that your notifications:

  • Have the same subject
  • Have reference headers that reference IDs seen earlier in the thread, or have references headers that consistently refer to the same message ID

Additionally, if you don’t want your messages to be threaded in Gmail, you can either have different subjects or send each message with a unique References header value that will never match another message.

Helpful links


Rollout details

G Suite editions
Available to all G Suite editions
On/off by default?
This feature will be ON by default.

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