Sending, receiving, and organizing email in Outlook on the web for business
Dear Jim,
Outlook on the web does support downloading all file attachments from a single email.
Try opening the message in a new window and testing in an InPrivate or Incognito browser window. If Download all is missing from every message containing multiple regular attachments, your organization’s download policy or browser security settings may be limiting the available actions. In that case, please reach out to your Microsoft 365 administrator to test the same message and review any policies that restrict file downloads from Outlook on the web. If you don't know who your IT administrator is, please refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support
I hope this helps. Looking forward to your reply.
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