Microsoft Starts Protecting Office 365 Users Against ‘Reply-All’ Email Storms

Microsoft is trying to eliminate 'reply-all' email storms in organisations by bringing a new feature to its Office 365 users. The feature, called the Reply-All Storm Protection, was announced at Microsoft Ignite 2019 in July last year and is now rolling out for large organisations to help IT teams reduce the impact of the reply-all storms that are common chiefly due to the negligence of employees. Reply-all storms often put pressure on email servers and result in a distributed denial-of-service (DDoS) attack.

As explained in a blog post, Microsoft is initially rolling out the Reply-All Storm Protection feature for email threads with more than 5,000 recipients that have generated over 10 reply-all sequences within an hour. The company has developed a dedicated non-delivery response (NDR) that will be delivered to the senders upon the feature comes into force. Subsequent replies in that case will also be blocked for four hours.

Microsoft will shows a dedicated non-delivery response (NDR) upon restricting email deliveries

Microsoft has plans to widen the scope of the Reply-All Storm Protection feature from the initial large organisations to smaller organisations based on the usage telemetry and customer feedback. This means that it is expected to be available to a broader range of Office 365 users over time.

However, since the new feature is limited to Office 365 and is designed for Exchange Online messaging platform, general users on Outlook.com and other email clients won't get its benefits.

Future enhancements possible
Although the Reply-All Storm Protection feature is initially based on the preset conditions designed by Microsoft, it is planned to receive future enhancements including the ability for IT administrators to add customisable thresholds and block duration. IT teams would also get reply-all storm reports and notifications through an update.

Already started helping Microsoft's teams
Interestingly, Microsoft is amongst the organisations that have faced a reply-all storm back in October 1997. A similar storm also impacted the Redmond company in January 2019 and even in March this year. The new feature is claimed to have helped the company reduce the impact of reply-all storms within its teams and is likely to help many other organisations in the coming days.

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