365 / Exchange Online MailBox Quota Limit

Title of the alert:  “MailBox Quota”

Description: Alerts if any mailboxes are reported as using over this percentage (of the Exchange Online Mailbox Quota). Percentage is taken as bytes used vs Quota Send Stop (ie, before there is an impact).


  • The percentage at which an alert is triggered can be set
  • It is possible to ignore specific users

The problem: This alert is triggered when the user account is close to the storage volume quota alert limit (ie, they are close to, or have used up too much of their email storage allowance for their given plan with 365)

Impact: If usage continues to increase, the ability to send, and then receive email will gradually be disabled in line with Microsoft policy.

Suggested steps: Engage a technician to confirm that the alert is accurate.   The technician can advise on suitable steps to resolve the quota issue (such as removing old emails, a plan upgrade, or another suitable approach depending on your specific requirements).