Find the Exchange Online limits for a variety of service areas, including address book limits, mailbox storage limits, and reporting and message trace limits, to name just a few.
The limits in Microsoft Exchange Online fall into one of the following categories:
Exchange Online Limits
| Address list limit | 1000 |
| Offline address book (OAB) limit | 250 |
| Address book policies (ABP) limit | 250 |
| Global address lists limit | 250 |
Mailbox folder limits across Hosted Exchange options
| Maximum number of messages per mailbox folder | 1 million |
| Warning for number of messages per mailbox folder | 900,000 |
| Maximum number of messages per folder in the Recoverable Items folder | 3 million |
| Warning for number of messages per folder in the Recoverable Items folder | 2.75 million |
| Maximum number of subfolders per mailbox folder | 10,000 |
| Warning for number of subfolders per mailbox folder | 900 |
| Maximum folder hierarchy depth | 300 |
| Warning for folder hierarchy depth | 250 |
| Maximum number of public folders | 100,000 |
| Maximum number of subfolders per public folder | 1,000 |
| Warning for number of subfolders per public folder | 900 |
Message limits
| Message size limit – Outlook | 50MB |
| Message size limit – OWA | 50MB |
| Message size limit – Outlook for Mac | 35 MB |
| Message size limit – migration | 50MB |
| Subject length limit | 255 characters |
| File attachments limit | 250 attachments |
| File attachment size limit – Outlook | 50MB |
| File attachment size limit – OWA | 25 MB |
| File attachment size limit – Outlook for Mac | 35 MB |
| Multipart message limit | 250 parts |
| Embedded message depth limit | 30 embedded messages |
Recipient and sender limits
| Recipient rate limit | 10,000 recipients per day |
| Recipient limit | 500 recipients |
Retention limits
| Deleted Items folder retention period | No limit |
| Retention period for items removed from the Deleted Items folder | 14 days |
| Junk Email folder retention period | 30 days |
Distribution group limits
| Maximum number of distribution group members | 100,000 members |
| Limit sending messages to large distribution group | 5,000 or more members |
| Maximum message size for large distribution groups | 10 MB |
Exchange ActiveSync limits
| Exchange ActiveSync device limit | 100 |
| Exchange ActiveSync device deletion limit | 20 |
| Exchange ActiveSync file attachment limit | 25 MB |
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