Hi @robynne,
Welcome to Microsoft Q&A, and thank you very much for reaching out.
Based on your description, I tested the scenario on my side and was able to reproduce the issue:
From my research, when replying or forwarding an HTML email that includes background color or stationery, Outlook preserves the original sender’s HTML formatting.
Unfortunately, as I checked, there is no global setting to disable this behavior, so manually removing the background is currently the only available option.
That said, from your screenshot, may I confirm whether the white box around the company logo and the google review in the signature is the main part that appears unprofessional?
If so, one practical workaround is to recreate your signature image using a transparent background, this can be done easily with background‑removal tools such as Microsoft Designer or similar alternatives. With a transparent background, the signature will remain clean and professional even when the surrounding email background changes.
For example:
I also understand how useful and convenient it would be to have a permanent setting for this. I recommend submitting this suggestion through the Microsoft Feedback Portal, where Microsoft engineering team actively reviews customer feedback to help guide future updates to the product. Feel free to share the feedback link here once submitted, the more voice a heard, the likely it is for this feature being considered in the future.
I hope this helps.
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