Office 365, Email, Exchange, Office 365 Exchange Limits
Various limits on Exchange Online
Office 365 Email Limits
- 100 GB mailbox quotas for users (50 GB for A1 Licenses)
- 50 GB mailbox quotas for unified groups
| Maximum number of messages per mailbox folder | 1 million |
|---|---|
| Maximum number of messages per folder in the Recoverable Items folder | 3 million |
| Storage quota for Recoverable Items folder | 100GB |
| Maximum number of subfolders per mailbox | 10,000 |
| Maximum folder hierarchy depth | 300 |
| Message size limit | 100 MB |
| Subject length limit | 255 characters |
| File attachments per message limit | 250 |
| Messages received | 3,600 per hour |
| Recipient rate limit | 10,000 recipients per day and up to 1000 an hour for Employee |
| Recipient rate limit (Resource Accounts and 2FA enabled Users) | 1,000 recipients per day and up to 500 an hour |
| Recipient rate limit (Non-2FA enabled Users) | 100 recipients per day and up to 50 an hour |
| Recipient limit | 500 per message |
| Message rate limit (SMTP client submission only) | 30 messages per minute |
| Maximum number of distribution group members | 50,000 |
| Maximum message size for large distribution groups (>5,000 members) | 2 MB |
| Exchange ActiveSync device limit | 100 |
| Exchange ActiveSync file attachment limit | 25 MB |
| smtp.office365.com max concurrent connections per mailbox limit | 3 |
| Junk Email folder retention period | 30 days |
| Password length limit for Outlook on the Web | 16 characters |
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