Showing my email history as ATT attachment

I login my company email to the Mail app via POP.

Current email format is Rich Text.

However I noticed that whenever I'm using Mail to reply an email, an ATT file will be attached whenever the recipient is Outlook user.

Please refer to the print screen below as how Outlook user sees my email:

I have tried converting Email Format to Plain Text, then the ATT file won't be there anymore.

But Plain Text has too many limitations in composing email.

Is there other alternatives to eliminate the ATT file?