If you haven't logged into your Microsoft account for a long time and you don't want it to be closed, now may be a good time to do so. The company has published a new document laying out its account activity policy, and it looks like you'll need to sign into your account at least once every two years in order to prevent it from being deleted. This change will be effective from August 30.
The current Microsoft Services Agreement, published in March of last year, gives users a five-year period to keep their account active. However, specific services, such as Outlook.com and OneDrive, have their own inactivity period of one year, counted separately from other Microsoft services.
With this change, it should be much easier for Microsoft to close existing inactive accounts, but there are some exceptions to safeguard users. If you've made any purchases on your Microsoft account, not including gift cards or expired subscriptions, your account won't be closed due to inactivity. If you have active subscriptions, unspent balance, or if you've published apps to the Microsoft Store, you'll also be safe. Parent accounts part of a family account will also not be closed as long as there are active minor accounts in the family.
Of course, two years is still a fairly long time to log into an account, and it's likely that you're not too interested in using it if you haven't signed in for that long. Nonetheless, if you were counting on the previous five-year period to keep your account running, you'll want to log in before the new policy comes into effect.