There are various service limits for Exchange Online that are designed to protect the service as a whole, our tenant, and detect anomalies such as compromised accounts. Listed below are high level limits that are most likely to be noticed by our user population, and for a complete list of limits, check the following link:
Exchange Online limits - Service Descriptions | Microsoft Docs
All active Students, Staff, and Faculty are on an E3 license plan. Alumni are E1, and inactive users aren't licensed. Shared/Resource mailboxes also do not receive a license since they are not directly logged into.
| Type | Limit | Notes |
|---|---|---|
| Message rate limiting | 30 email submissions per minute, per mailbox | There are no overrides for this. No sent messages are lost or denied, they will sit in users outbox until the next minute and send as many as possible. |
| Recipient rate limiting | 10000 recipients every 24 hours, per mailbox | Specifies the total number of email addresses which can be mailed to in a 24 hour period, whether unique or not. |
| Receive rate limit | 3,600 messages per hour, per mailbox | |
| User mailbox storage | 100gb (active staff/faculty/student mailboxes) |
|
| Shared/resource mailbox storage | 50gb | |
| Alumni mailbox storage | 50gb | |
| Archive mailbox storage | Unlimited | Available only for E3 licensed mailboxes |
| Messages per mailbox folder | 1 million | |
| Folders per mailbox | 10,000 | |
| Message size limit | 50mb | This includes attachments, but does not account for mime encoding or client limits. |
| Junk mail folder retention | 30 days | |
| Deleted Items retention | 90 days | Deleted items are recoverable for 30 days after removal from Deleted Items folder. |
| Inbox Forwarding Rule limit | 10 Forwardee limit | The maximum number of recipients that can be configured for an inbox or transport rule with a redirecting action. |