Is this a change you are reporting? A new behavior to something you’ve done before? Or are you doing something you’ve not done before and expecting a different behavior than you are seeing?
This sometimes happens depending on the email client you are using. Outlook is notoriously hard to work with.
We will often edit replies we receive by email to fix formatting or to remove extraneous text.
The only want to be certain is to edit your email before sending to remove the content you don’t want to have posted.