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: 100 GB
- 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 500 an hour for Employee
- Recipient rate limit: 1,000 recipients per day and up to 500 an hour for Resource Accounts and 2FA enabled Users
- Recipient rate limit: 100 recipients per day and up to 50 an hour for Non-2FA enabled Users
- 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