Outlook Mailbox Full or Over Quota
Outlook Mailbox Full or Over Quota
When a work or school mailbox reaches its storage limit, Outlook warns that it is nearly full or over quota. Once capacity is exceeded, you may be unable to send or receive messages, and senders may receive a mailbox-full error. Your organization's configured quota may differ from Microsoft's maximum, so rely on the storage page shown for your account.
Check what is using space
In new Outlook, select Settings > Accounts > Storage. In Outlook on the web, select Settings > Account > Storage. The page shows total usage and a folder-by-folder breakdown. In classic Outlook, choose File > Tools > Mailbox Cleanup to view mailbox and folder sizes and to find older or larger items.
Before deleting anything, identify messages that must be kept for legal, regulatory, project, or business reasons. Follow your organization's records-retention policy. Do not move corporate mail to a personal account, USB drive, or unapproved cloud service.
Free space safely
- Start with obvious disposable items. Review Junk Email and Deleted Items, then empty them when you are sure the contents are no longer needed. Deleted Items continues to count against the quota until it is emptied.
- Find large messages. In Outlook on the web or new Outlook, sort or filter the message list by size. Review messages with large attachments in Inbox and Sent Items.
- Save required attachments in an approved location. If policy permits, save business attachments to the correct OneDrive or SharePoint library, verify that the saved file opens and has appropriate permissions, then delete the original message only if the email itself is no longer a required record.
- Remove old, low-value mail in batches. Use the Storage page's folder cleanup choices or Outlook search to target a date range or sender. Review the selection before permanently deleting it.
- Use Sweep carefully. Sweep can remove recurring mail from a sender or keep only recent messages. Items moved to Deleted Items will not reduce usage until that folder is emptied.
- Use Archive only when appropriate. Moving an item to the ordinary Archive folder may not reduce server mailbox usage. An organization-provided Online Archive is different and can reduce primary mailbox usage. If you are unsure which archive you have, ask IT before moving large volumes.
In classic Outlook, Mailbox Cleanup can find messages older than a chosen date or larger than a chosen size. It also shows Deleted Items and Conflicts folder size. Avoid creating a local PST as a quick fix unless your organization specifically permits it; local archives can be difficult to back up, search, retain, and access from other devices.
After cleanup
Allow time for the storage figure to update, then refresh the Storage page. Close and reopen Outlook and send a small test message to yourself. If you were over quota, delayed inbound messages may arrive after the service recognizes available space. Ask an external sender to retry only after capacity is available; do not assume every previously rejected message will be delivered automatically.
If the quota does not decrease, check that Deleted Items was emptied and that the large messages were removed from all relevant folders. Do not repeatedly purge Recoverable Items or change retention settings; those controls may be managed for compliance.
When to contact support
Contact your IT help desk if the mailbox remains over quota after reasonable cleanup, the Storage page is unavailable, an Online Archive is expected but missing, retention rules prevent deletion, or business records make cleanup unsafe. Only administrators can review or change an organization-assigned quota or provision additional archive capacity.
Provide your mailbox address, screenshot of the storage breakdown with sensitive subjects hidden, current usage/quota, folders consuming the most space, cleanup already performed, and the exact warning or non-delivery message. Mention any legal hold or retention requirement you know applies.