What happens when a mailbox goes over quota

On this page:

See also: What is my quota on the Exchange server? How do I check my Exchange email quota? How do I manage my email quota?

Exchange mailbox

• Exchange mailboxes have two quotas, a soft lower quota and an hard upper quota.
• Users with mailboxes approaching the lower quota limit will receive a warning notification via email. Some mail programs display a quota warning message onscreen, but others do not and rely on your noticing the email reminder.
• An account that exceeds the lower quota limit will not be able to send mail (but see Commentary). Attempts to send mail will show an error message. Incoming mail can still be received, as long as the account has not yet exceeded the upper quota limit.
• You must delete items to get below the quota limit to be able to resume sending mail. Note that messages in your Deleted Items folder still count against your quota. You must get them out of your Deleted Items folder, by shift-deleting individual items or by emptying the whole Deleted Items folder.
• An account that exceeds the upper quota limit will be blocked from receiving mail and from storing new messages. Your account will not be able to send mail and will not be able to receive mail.
• New mail addressed to an account that is over the upper quota may be immediately returned to the sender with an error message, without being stored for delivery attempts.

Commentary

• The soft quota limit, the "send limit", only blocks accounts that use full Exchange clients to send mail from within Exchange. A mail client that communicates with the Exchange server's IMAP port (like pre-10.6 Apple Mail or like Evolution) will send mail through an SMTP connection to outgoing.mit.edu, and will not be affected by the Exchange send limit. IMAP-based Exchange clients will still see the warning message that the server delivers to the mailbox..

• At the time of writing (March 2016),Exchange mailboxes have a 15 GB soft quota (send limit),
  and a slightly higher hard quota (receive limit).

Screen shots

Here are screen shots illustrating how selected mail programs behave as you approach your mail quota limits.

Mail warning received when your Exchange account approaches its quota:

You will get this warning in your email when your account approaches the lower quota limit, the send limit. The screen shot shows an account that is using 2000 MB of its 2048MB quota.

Exchange account, reading mail with OWA:

OWA shows the quota notification in the upper-left part of the web page.

Warning displayed when your Exchange account approaches its quota:

Message displayed when your Exchange account exceeds the quota and cannot send:

Message displayed when your Exchange account exceeds the hard upper limit and cannot receive:

Exchange account, blocked from sending mail from OWA Light because of quota:

OWA Light does not show quota notifications on-screen, but does show an error if you are blocked from sending mail because of being over your send limit:

Exchange account, warning displayed in Outlook (2019 and 2016) when over quota:

Outlook (2019 and 2016) will detect when your account is over quota, and may open the Mailbox Cleanup tool at period intervals.

If you try to send mail while over quota, Outlook (2019 and 2016) will show an error and the mail will not go out: