Office 365, Email, Exchange, Office 365 Exchange 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