Receiving limits apply to the number of messages that a user, group, or public folder can receive per hour. This applies for both messages received from the internet and from on-premises servers. When the receiving limit has been exceeded, any emails sent to that mailbox will receive a non-delivery report stating that the mailbox has exceeded the maximum delivery threshold. After one hour, the limit will refresh and the mailbox will once again be able to receive messages.
|Feature||Microsoft 365 Business Basic||Microsoft 365 Business Standard Office||Office 365 Enterprise E1||Office 365 Enterprise E3||Office 365 Enterprise E5||Office 365 Enterprise F3|
|Messages received||3,600 messages per hour||3,600 messages per hour||3,600 messages per hour||3,600 messages per hour||3600 messages per hour||3600 messages per hour|
Sending limits apply to the number of recipients, number of messages, and number of recipients per message that a user can send from their Exchange Online account.
For distribution groups stored in an organization's address book, the group is counted as one recipient. For distribution groups stored in the Contacts folder of a mailbox, the members of the group are counted individually.
Recipient rate limit: To discourage the delivery of unsolicited bulk messages, Exchange Online has recipient limits that prevent users and applications from sending large volumes of email. These limits are applied per-user to all outbound and internal messages.
Exchange Online customers who need to send legitimate bulk commercial email (for example, customer newsletters) should use third-party providers that specialize in these services.
Recipient limit: This is the maximum number of recipients allowed in the To:, Cc:, and Bcc: fields for a single email message.
For the purposes of the recipient rate limit and the recipient limit, a distribution group that is stored in the organization's shared address book counts as one recipient. In a personal distribution list, each recipient is counted separately.
Recipient proxy address limit: The recipient proxy address limit is the maximum number of aliases (email addresses) that a recipient mailbox can have.
Message rate limit: Message rate limits determine how many messages a user can send from their Exchange Online account within a specified period of time. This limit helps prevent over consumption of system resources by a single sender. If a user submits messages at a rate that exceeds the limit via SMTP client submission, the messages will be rejected and the client will need to retry.
|Feature||Microsoft 365 Business Basic||Microsoft 365 Business Standard||Office 365 Enterprise E1||Office 365 Enterprise E3||Office 365 Enterprise E5||Office 365 Enterprise F3|
|Recipient rate limit1||10,000 recipients per day||10,000 recipients per day||10,000 recipients per day||10,000 recipients per day||10,000 recipients per day||10,000 recipients per day|
|Recipient limit2||Customizable up to 1000 recipients||Customizable up to 1000 recipients||Customizable up to 1000 recipients||Customizable up to 1000 recipients||Customizable up to 1000 recipients||Customizable up to 1000 recipients|
|Recipient proxy address limit||400||400||400||400||400||400|
|Message rate limit||30 messages per minute||30 messages per minute||30 messages per minute||30 messages per minute||30 messages per minute||30 messages per minute|
1 After the recipient rate limit is reached, messages can't be sent from the mailbox until the number of recipients that were sent messages in the past 24 hours drops below the limit. For example, a user sends an email message to 5000 recipients at 09:00 AM, then sends another message to 2500 recipients at 10:00 AM, and then sends another message to 2500 recipients at 11:00 AM, hitting the limit of 10,000 messages. The user won't be able to send messages again until 09:00 AM the next day. 2 You can customize recipient limits between 1 and 1000 for existing mailboxes and for new mailboxes that will be created in the future. Edit the recipient limit on existing mailboxes individually or in bulk using the Exchange admin center and customize the default setting for new mailboxes via Remote PowerShell. For more information, see Customizable recipient limits in Office 365.