Sometimes you need to Reply to an existing Email in Gmail but want to change the Subject Line - but changing it in Gmail is not a well-known feature - Learn How!

A well-defined Email Subject Line helps ensure that the purpose and goal of your Email message is quickly communicated and understood by the message recipient.

Conversation Threads - A Quick Primer

But the Email Subject Line serves as more than just a high-level summary of the message.

The Email Subject Line is also the way that “Conversation Threads” operate in most Email Systems.

A “Conversation Thread” is a set of messages that are grouped by their common Subject Line.

Whenever you “Reply” to an Email, your message will automatically be grouped as a “thread” that is part of that same “message chain” based on the same Subject Line.

Conversation Threads in Outlook

In Microsoft Outlook, Emails with the same Subject Line can be viewed as a single “thread” if you choose the “Conversation View” in your Inbox.

But each Email is still an individual Email, and they are just “Grouped” for viewing purposes.

Conversation Threads in Gmail

But Gmail handles things a bit differently than Outlook….

In Gmail, all the messages under the same Subject are actually part of one, long message. All the various “replies” and “responses” all make up that single, long Email chain under that single Subject Line.

This means that in Gmail, you do not need to set a special “view” to see your “conversation threads” as you do in Microsoft Outlook.

But sometimes, you may want to change the “Subject Line” to reflect a new issue or topic, but wish to keep the prior replies as reference to the message.

This may happen if the message concerns the same people but the issue has changed and the old Subject line no longer applies.

Luckily, there is a way to do this in Gmail, although it is not well known.

We can do this by changing the Subject Line of the message, which will still have all the old messages as quoted replies.

Steps to Change the Gmail Subject Line:

To Reply or Forward an Email in an existing Message Thread with a new Subject Line, but keeping all the original Emails in the same Thread, follow these steps:

1) Find your Email that contains your conversation thread in your Inbox and Open that Email.

2) Select “Reply” at the bottom of the Email. 

3) It will then open your “reply window” for you to enter your reply at the bottom of the screen.

4) Click the little “Down Arrow” that is located at the top-left of the message box and select “Edit Subject”. 

5) A new “compose” window will then appear and the “Subject Line” will be shown in “Edit Mode”.

6) Update the Subject Line and change it to something that makes sense for your new message thread.

7) “Send” your message. 

All the previous Emails will be included, but you will now have a “new thread” that is linked to this new Subject Line, and all future Emails will now be part of this new conversation thread.

Since Gmail keeps mail together in a single conversation thread based on the Subject Line, the recipients will now receive a NEW Mail message with the UPDATED Subject Line, but containing the old conversation history. 

This may be a bit confusing to the recipient, so you may wish to note to the recipient that you have updated the Subject Line to reflect a new issue that needs to be tracked separately.

IMPORTANT TIP:  You can also use these same steps when you want to either “Reply All” or “Forward” a message with a new Subject Line.  Just follow these same steps for updating the Subject.

Did you know how to change the Gmail Subject Line?

Do you update the Subject Line when needed?

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