Exchange Online

Exchange Online is the cloud email and calendaring service in Microsoft 365. It hosts user mailboxes (typically 50 or 100 GB), shared mailboxes, distribution lists, room and equipment mailboxes, and the calendars that surface in Outlook and Teams. Mail flow rules, anti-spam and anti-malware filtering, mailbox retention, and litigation hold all run inside Exchange Online. It works with Outlook on Windows, Mac, web, and mobile, and with the native mail clients on iOS and macOS via standard protocols. Exchange Online is the cloud counterpart to the on-premises Exchange Server; the two can run side-by-side in hybrid deployments.