Exchange Online will start archiving your oldest emails before your inbox bursts

Microsoft's latest attempt to make the dreaded "mailbox full" response a thing of the past is rolling out in October and November. Threshold-based auto-archiving is coming to Exchange Online.

The plan, which Microsoft refers to as "reimagining archiving," involves automatically moving the oldest items from a user's primary mailbox to an archive location when the mailbox approaches 90 percent of its quota.

Time-based archive policies – such as "move to archive after two years" – are useful for some, but can't keep up with increasing volumes of incoming emails, large attachments, and the relentless tsunami of AI-generated content (Microsoft cites Copilot as an example, which will generate emails containing meeting notes, automated reports, notifications, and so on).

"As a result, mailboxes can reach full capacity before time-based archiving kicks in, leading to functional loss such as inability to send or receive emails directly impacting business continuity and operational efficiency ...