Sending, receiving, and organizing email in Outlook.com
For Outlook.com, the documented limits for Microsoft 365 subscribers are:
- Daily recipients: 5,000
- Maximum recipients per message: 500
- Daily non-relationship recipients: 1,000
A non-relationship recipient is someone never emailed before. Limits can also be lower for non-subscribers and can vary based on usage history. New Outlook.com accounts can have a temporarily lower sending quota until credibility is established.
If sending was blocked even though the total appears well under 5,000, the most relevant Outlook.com guidance is to improve account trust and sending patterns:
- Make sure account info is fully updated: phone number, alternate email, profile details.
- Use a strong password with upper/lowercase letters, numbers, and special characters.
- Add recipients to Contacts in Outlook.com.
- Communicate frequently with Contacts so they become established relationship recipients.
- Use the Microsoft Authenticator app to verify identity.
- If sending to groups repeatedly, split mail into smaller batches and avoid sending many messages rapidly, since temporary blocks can still occur.
Other things to check when mail is blocked:
- Attachment size: Outlook.com can’t send messages with attachments larger than 25 MB.
- Signature issues: if the message has a signature, remove it and try again.
- If a recipient address is correct but a non-delivery report was received, use Sender Support in Outlook.com.
Since this has happened more than once, the most practical way to use Outlook.com more efficiently is:
- keep recipients in Contacts,
- send to smaller groups,
- spread sends out over time,
- avoid sudden spikes in outbound mail,
- make sure the account profile and security details are complete.