Information on Exchange Online limits is provided by Microsoft and summarized below.
| Feature | Office 365 | Exchange 2010 |
| User Mailbox | 50 GB | 4GB |
| Message size limit (including attachments) | 100 MB | 100 MB |
| OWA/Outlook for Mac File attachment size limit | 25/35 MB | 25 MB |
| Recipient limit | 500 recipients | 500 recipients |
| Deleted Items folder retention | No Limit | No Limit |
| Junk email folder retention | 30 days | 2 years |
| Retention after trash is emptied | 14 days | 14 days |
| Mailbox Backup | Replicated 4x in cloud | |
| Disaster Recovery of mailboxes | Mailboxes will remain accessible in the cloud |