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Does M365 de-duplicate Outlook email attachements?

LEE JOO LEONG 20 Reputation points
2026-03-11T09:03:01.7666667+00:00

Does M365 de-duplicate Outlook email attachments within the same organization?

Exchange Online
Exchange Online

A cloud-based service included in Microsoft 365, delivering scalable messaging and collaboration features with simplified management and automatic updates.

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  1. Q&A Assist
    2026-03-11T09:03:10.06+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    The provided information does not state that Microsoft 365 or Exchange Online performs any cross‑message or cross‑mailbox de‑duplication of Outlook email attachments within the same organization. The only documented de‑duplication behavior in the context is at the Dynamics 365 Dataverse level for email attachments, where a single file BLOB can be reused by multiple email or template records via ActivityMimeAttachment.AttachmentId, but this is specific to Dynamics 365 email activity tables, not general Outlook/Exchange Online storage.

    Based on the context, no general M365/Exchange Online attachment de‑duplication mechanism is described.

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