Illustration by Alex Castro / The Verge

Microsoft is rolling out a new reply-all protection feature for Office 365 and Exchange Online. It’s designed to prevent email storms (reply allpocalypse), when hundreds or thousands of people start replying to an email thread after someone forgot to BCC everyone or a distribution list was misconfigured.

The new block feature will mostly benefit large organizations, and is initially being rolled out to detect 10 reply-all emails to over 5,000 recipients within 60 minutes. “Over time, as we gather usage telemetry and customer feedback, we expect to tweak, fine-tune, and enhance the Reply All Storm Protection feature to make it even more valuable to a broader range of Office 365 customers,” explains Microsoft’s Exchange transport team.

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