Microsoft rolled out a “Reply-All Storm Protection” feature for Office 365 users. It was announced in 2019 at Microsoft’s Microsoft Ignite 2019 event.
When a user chooses Reply-All to a mail, which has a large number of recipients, then it may slow down or crash the server. This feature will help IT staff to stop such email storms and prevent the organization’s server to slow down or crash.
Microsoft “Reply-All Storm Protection” will only work if it detects 10 replies all-s to over 5,000 recipients within 60 minutes. It will then block all the replies to the thread for the next 4 hours. Microsoft said it will keep refined and fine-tune the feature over time.