Message, Mailbox, and Recipient Limits

After you enroll your organization in Outlook Live, users may have the following questions that directly affect their e-mail experience:

  • Are any sending size limits applied to e-mail messages?
  • What recipient limits are applied to e-mail messages?
  • Does my Outlook Live organization have a mailbox quota?

The limits on messages, mailboxes, recipients, and e-mail clients fall into one of the following categories:

You can't modify these limits, but you and your users should be aware of them.

Message limits

These limits are applied to every e-mail message.

Message limit Value

Message size limit   The maximum total size of an e-mail message. The total size includes the message header, the message body, and any file attachments.

25 MB

File attachment size limit   The maximum allowed size of a single file attachment in an e-mail message. The message may contain many attachments that greatly increase the overall size of the message. However, the attachment size limit only applies to the size of an individual attachment.

18 MB

File attachments limit   The maximum number of file attachments allowed in an e-mail message. Even if the total size of all the file attachments doesn't violate the message size limit, there is still a limit on how many attachments are allowed in the message.

125 attachments

Subject length limit   The maximum number of text characters allowed in the subject line of an e-mail message.

255 characters

Multipart message limit   The maximum number of message body parts that are allowed in a MIME multipart message.

250 parts

Embedded message depth limit   The maximum number of forwarded e-mail messages that are allowed in an e-mail message.

30 embedded messages

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Mailbox limits

These limits are applied to every mailbox.

Mailbox limit Value

Mailbox quota   The maximum allowable size of a mailbox.

10 GB

Issue a mailbox quota message   When a mailbox reaches the size specified by this limit, a warning message is displayed.

9 GB

Prohibit send   When a mailbox reaches the size specified by this limit, no e-mail messages can be sent from the mailbox. Any attempt to send messages from a mailbox that has reached this size will generate an error message that explains the limit.

9.668 GB

Prohibit receive   When a mailbox reaches the size specified by this limit, no e-mail messages can be successfully delivered to the mailbox. Any messages that are sent to a mailbox that has reached this size are returned to the sender with an error message that explains the limit.

9.668 GB

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Recipient and sender limits

These limits are applied to messages, senders, or recipients to combat spam and mass-mailing worms or viruses.

Limit Value

Recipient limit   The maximum number of message recipients allowed in the To:, Cc:, and Bcc: fields. A public group is counted as a single recipient.

100 recipients

Message rate limit   The maximum number of e-mail messages that can be sent from a single Outlook Live e-mail client per minute. The client is identified by its IP address.

30 message per minute

Recipient rate limit   The maximum number of recipients that can receive e-mail messages sent from a single Outlook Live e-mail account per day.

250 recipients per day

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Retention limits

These limits control the amount of time that items in specific folders in the Inbox are accessible.

Retention limit Value

Deleted Items folder retention period   The maximum number of days that items can remain in the Deleted Items folder before they are automatically removed.

Unlimited

Retention period for items removed from the Deleted Items folder   the maximum numbers of days that items removed from the Deleted Items folder are retained before they are permanently deleted.

14 days

Junk E-mail folder retention period   The maximum number of days that items can remain in the Junk E-mail folder before they are automatically removed.

30 days

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