There are various service limits for Exchange Online SUMail that are designed to protect the email service as a whole , our tenant, and detect anomalies such as compromised accounts. Listed below are high level The following list breaks out limits that are would most likely to be noticed by our user populationaffect all email users, and for a complete list of service limits , check the following link:
Exchange Online limits - Service Descriptions | Microsoft Docs
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| 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 | |
| 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. |