SMTP server smtp.live.com inserts updated Return-Path: email address but uknown/invalid Sender: email address after outlook account rename

Return-Path: <*** Email address is removed for privacy ***>

From:  *** Email address is removed for privacy ***

Sender: *** Email address is removed for privacy ***

as does Gmail.

Some email software receiving emails like this will reply to *** Email address is removed for privacy *** rather than the external email address, *** Email address is removed for privacy ***.

I have experienced this myself. Of course I want to avoid this.

Outlook.com supports the facility to rename the *** Email address is removed for privacy *** account to *** Email address is removed for privacy ***.

This seemed to offer the option of standardising all three headers as *** Email address is removed for privacy ***.

So I implemented this rename, which itself caused some problems, especially resetting all my send and receive external email accounts to send only, though still listing them as send and receive. I understand from this forum that many users have lost their emails doing the rename. However I keep my email on a local client so that could not happen.

After the rename, I get these headers:

I made up this number rather than printing the one I got, but this hex number is in exactly the same format.

The original address *** Email address is removed for privacy *** does not feature.

Sending to this *** Email address is removed for privacy *** email address gets the reply:

Where did this Sender: header come from?

Why is it not *** Email address is removed for privacy *** or at least *** Email address is removed for privacy ***?

Thanks