Dear @Jason Boardman,
Thank you for posting your question in the Microsoft Q&A forum.
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Based on your description, you set up an email signature with a logo in Outlook, but when composing or replying to emails, only the text appears while the image is missing.
I have tested inserting an image into a signature, and it worked correctly in my test environment.
Could you please share how you created the signature on your side so I can better understand your situation?
In the meantime, to insert an image into a signature, you can follow the steps below:
Log in your business account in Outlook
Click New message > in the pane menu > Insert tab > Signature > add your signature, then you can insert your image in your signature.
Please let me know if it works on your side. If you encounter any issues or get stuck at any step, feel free to let me know so I can support you more effectively.
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