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Dear Jedthedog,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, it seems that you are trying to drag the email into SharePoint, however, lose attachments.
We've also done a quick test, if we upload a downloaded email directly to SharePoint, and open it in browser, the attachment will be shown as text, if we download the email to local device and open, the attachment is there as expected.
If the understanding above is right, per the test and searching, we're afraid that there's no out of box way in SharePoint to achieve this requirement currently. Sorry for the inconvenience caused.
There's a possibility that this can be achieved by Power Automate as a workaround, we've found a similar thread for your reference: Email with attachment from outlook 365 to sharepoint online - Microsoft Q&A
If you want to know more about Power Automate solutions, considering that we have a dedicated channel Microsoft Power Automate Community, for you to be assisted properly, we sincerely recommend you go to that community and post a new thread. You can click "Start a topic" to post a question there, as shown below.
Members and engineers over there are proficient in the knowledge of creating customized flow queries. They will focus on the specific situation on your side and share suggestions for you. We are sure that our experts from that team can address your query effectively and accurately.
If the scenario above is not consistent with yours, you can also post back and point that.
Your patience and understanding are highly appreciated. I hope that you are keeping safe and well!
Sincerely,
Rhoda | Microsoft Community Moderator