Exchange online (Outlook) Limits

This article details microsoft exchange online Limits

Find the Exchange Online limits for a variety of service areas, including address book limits, mailbox storage limits, and reporting and message trace limits, to name just a few.

The limits in Microsoft Exchange Online fit into one of the following categories:





These limits are intended to limit mailboxes to known dimensions that can be supported in Exchange Online. The goal of these limits is to prevent an infinite number of mailbox items per folder, an infinite number of folders per mailbox, or an infinite number of public folders per Exchange Online organization. For practical purposes, mailbox folder limits are in effect unlimited and sufficient to support most Exchange Online mailboxes and on-premises mailboxes that are migrated to Exchange Online.
  • Maximum number of messages per mailbox folder Specifies the maximum number of messages for a mailbox folder. New messages can't be delivered or saved in a folder when this limit is reached.
  • Warning for number of messages per mailbox folder Specifies the number of messages that a mailbox folder can hold before Exchange Online sends a warning message to the mailbox owner. When this quota is reached, warning messages are sent once a day.
  • Maximum number of messages per folder in the Recoverable Items folder Specifies the maximum number of messages that can be contained in each folder in the Recoverable Items folder. When a folder exceeds this limit, it can't store new messages. For example, if the Deletions folder in the Recoverable Items folder has exceeded the message count limit and the mailbox owner attempts to permanently delete items from their mailbox, the deletion will fail.
  • Warning for number of messages per folder in the Recoverable Items folder Specifies the number of messages that each folder in the Recoverable Items folder can hold before Exchange Online logs an event to the application event log.

  • Maximum number of subfolders per mailbox folder Specifies the maximum number of subfolders that can be created in a mailbox folder. The mailbox owner won't be able to create a new subfolder when this limit is reached.

  • Warning for number of subfolders per mailbox folder Specifies the number of subfolders that can be created in a mailbox folder before Exchange Online sends a warning message to the mailbox owner. When this quota is reached, warning messages are sent once a day.
  • Maximum folder hierarchy depth Specifies the maximum number of levels in the folder hierarchy of a mailbox. The mailbox owner won't be able to create another level in the folder hierarchy of the mailbox folder when this limit is reached.
  • Warning for folder hierarchy depth Specifies the number of levels in the folder hierarchy of a mailbox folder that can be created before Exchange Online sends a warning message to the mailbox owner. When this quota is reached, warning messages are sent once a day.
  • Maximum number of public folders Specifies the maximum number of public folders in the complete public folder hierarchy. When this limit is reached, existing public folders must be deleted before new public folders can be created.
  • Maximum number of subfolders per public folder Specifies the maximum number of subfolders that can be created in a public folder. New subfolders can't be created in a public folder when this limit is reached.
  • Warning for number of subfolders per public folder Specifies the number of subfolders that can be created in a public folder before Exchange Online sends a warning message to the folder owner. If no owner exists, warning messages are sent to users with Owner permissions. When this quota is reached, warning messages are sent once a day.

Mailbox folder limits across Office 365 options

Feature 
Office 365 Business Essentials 
Office 365 Business Premium 
Office 365 Enterprise E1 
Office 365 Enterprise E3 
Office 365 Enterprise E5 
Office 365 Enterprise F1 
Maximum number of messages per mailbox folder 
1 million 
1 million 
1 million 
1 million 
1 million 
1 million 
Warning for number of messages per mailbox folder 
900,000 
900,000 
900,000 
900,000 
900,000 
900,000 
Maximum number of messages per folder in the Recoverable Items folder 
3 million 
3 million 
3 million 
3 million 
3 million 
3 million 
Storage quota for Recoverable Items folder in primary mailbox (not on hold) 
30 GB 
30 GB 
30 GB 
30 GB 
30 GB 
30 GB 
Storage quota for Recoverable Items folder in primary mailbox (on hold) 
100 GB 
100 GB 
100 GB 
100 GB 
100 GB 
100 GB 
Storage quota for Recoverable Items folder in archive mailbox (not on hold) 
30 GB 
30 GB 
30 GB 
Unlimited2
Unlimited2
30 GB 
Storage quota for Recoverable Items folder in archive mailbox (on hold) 
100 GB1 
100 GB1 
100 GB1 
Unlimited2
Unlimited2
100 GB1 
Warning for number of messages per folder in the Recoverable Items folder 
2.75 million 
2.75 million 
2.75 million 
2.75 million 
2.75 million 
2.75 million 
Maximum number of subfolders per mailbox folder 
10,000 
10,000 
10,000 
10,000 
10,000 
10,000 
Warning for number of subfolders per mailbox folder 
9000 
9000 
9000 
9000 
9000 
9000 
Maximum folder hierarchy depth 
300 
300 
300 
300 
300 
300 
Warning for folder hierarchy depth 
250 
250 
250 
250 
250 
250 
Maximum number of public folders 
500,000 
500,000 
500,000 
500,000 
500,000 
Not available 
Maximum number of subfolders per public folder 
10,000 
10,000 
10,000 
10,000 
10,000 
Not available 
Warning for number of subfolders per public folder 
9000 
9000 
9000 
9000 
9000 
Not available 

 Note

1 This is the storage quota for the Recoverable Items folder, not the quota for the entire archive mailbox. The storage quota for the archive mailbox is unlimited for users with an Exchange Online Plan 2 license or for users who have both an Exchange Online Plan 1 and an Exchange Online Archiving license. For information about increasing the Recoverable Items quota, see Increase the Recoverable Items quota for mailboxes on hold. 


2 The initial storage quota for the Recoverable Items folder in an archive mailbox is 100 GB. When auto-expanding archiving is turned on, additional storage is automatically added when the storage capacity for the Recoverable Items folder is reached. For more information, see Overview of unlimited archiving in Office 365. See the Office 365 Roadmap for details about availability of auto-expanding archiving.

Mailbox folder limits across standalone plans

Feature 
Exchange Server 2013 
Exchange Online Plan 1 
Exchange Online Plan 2 
Exchange Online Kiosk 
Maximum number of messages per mailbox folder 
No limit1 
1 million 
1 million 
1 million 
Warning for number of messages per mailbox folder
No limit 
900,000 
900,000 
900,000 
Maximum number of messages per folder in the Recoverable Items folder 
No limit 
3 million 
3 million 
3 million 
Storage quota for Recoverable Items folder in primary mailbox (not on hold) 
30 GB 
30 GB 
30 GB 
30 GB 
Storage quota for Recoverable Items folder in primary mailbox (on hold) 
100 GB 
100 GB 
100 GB 
100 GB 
Storage quota for Recoverable Items folder in archive mailbox (not on hold) 
30 GB 
30 GB 
30 GB 
30 GB 
Storage quota for Recoverable Items folder in archive mailbox (on hold) 
100 GB2 
100 GB2 
Unlimited3 
Unlimited3 
Warning for number of messages per folder in the Recoverable Items folder 
No limit 
2.75 million 
2.75 million 
2.75 million 
Maximum number of subfolders per mailbox folder 
No limit 
1000 
1000 
1000 
Warning for number of subfolders per mailbox folder 
No limit 
900 
900 
900 
Maximum folder hierarchy depth 
No limit 
300 
300 
300 
Warning for folder hierarchy depth 
No limit 
250 
250 
250 
Maximum number of public folders 
1,000,000 
100,000 
100,000 
Not available 
Maximum number of subfolders per public folder 
N/A 
1,000 
1,000 
Not available 
Warning for number of subfolders per public folder 
N/A 
900 
900 
Not available 

 Note

1 Microsoft recommends no more than 1,000,000 messages per mailbox folder. > 


2 This is the storage quota for the Recoverable Items folder, not the quota for the entire archive mailbox. The storage quota for the archive mailbox is unlimited for users with an Exchange Online Plan 2 license or for users who have both an Exchange Online Plan 1 and an Exchange Online Archiving license. For information about increasing the Recoverable Items quota, see Increase the Recoverable Items quota for mailboxes on hold


3 The initial storage quota for the Recoverable Items folder in an archive mailbox is 100 GB. When auto-expanding archiving is turned on, additional storage is automatically added when the storage capacity for the Recoverable Items folder is reached. For more information, see . See the Office 365 Roadmap for details about availability of auto-expanding archiving.

Message limits

The following limits are applied to every email message.

  • Message size limit Message size limits are necessary to prevent large messages from blocking delivery of other messages and affecting service performance for all users. These limits include attachments, and apply organization-wide to all messages (inbound, outbound, and internal). Messages larger than this limit will not be delivered, and the sender will receive a non-delivery report (NDR). While message size limits can be configured up, down, or on a per-user basis, administrators can also create transport rules to limit the maximum size of any individual attachment. To learn more, see Office 365 now supports larger email messages.

Note: Particular email clients may have lower message size limits or may limit the size of an individual file attachment to a value that is less than the Exchange Online message size limit.

  • Message header size limit Specifies the maximum size of all message header fields in a message. The current limit is 256 KB. If the total size of all message headers exceeds 256 KB, Exchange Online will reject the message with error "552 5.3.4 Header size exceeds fixed maximum size." The size of the message body or attachments isn't considered. Because the header fields are plain text, the size of the header is determined by the number of characters in each header field and by the total number of header fields. Each text character consumes 1 byte.
  • Subject length limit The maximum number of text characters allowed in the subject line of an email message.
  • File attachments limit The maximum number of file attachments allowed in an email 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. This limit is controlled by the multipart message limit.
  • File attachment size limit The maximum file size of a single attachment.

 Note: This is the maximum file size of a single attachment. Individual client programs, including Outlook Web App, may limit the size of attachments below this maximum. Exchange ActiveSync does not implement attachment size limits on an individual attachment basis. The total size of all attachments to an Exchange ActiveSync message must be less than the message size limit.

  • Multipart message limit The maximum number of message body parts that are allowed in a MIME multipart message. This limit also controls the maximum number of file attachments that are allowed in a message.
  • Embedded message depth limit The maximum number of forwarded email messages that are allowed in an email message.

Message limits across Office 365 options

Feature 
Office 365 Business Essentials 
Office 365 Business Premium 
Office 365 Enterprise E1 
Office 365 Enterprise E3 
Office 365 Enterprise E5 
Office 365 Enterprise F1 
Message size limit - Outlook 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
Message size limit - OWA 
112 MB1, 3 
112 MB1, 3 
112 MB1, 3 
112 MB1, 3 
112 MB1, 3 
112 MB1, 3 
Message size limit - Outlook for Mac 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
150 MB1, 2 
Message size limit - migration 
150 MB 4 
150 MB 4 
150 MB 4 
150 MB 4 
150 MB 4 
150 MB 4 
Size limit for encrypted messages (for subscribers using Office 365 Message Encryption with new capabilities)5 
150 MB 
150 MB 
150 MB 
150 MB 
150 MB 
150 MB 
Size limit for encrypted messages (for subscribers using Office 365 Message Encryption legacy version)5 
25 MB 
25 MB 
25 MB 
25 MB 
25 MB 
25 MB 
Subject length limit 
255 characters 
255 characters 
255 characters 
255 characters 
255 characters 
255 characters 
File attachments limit 
250 attachments
250 attachments
250 attachments
250 attachments
250 attachments
250 attachments
File attachment size limit - Outlook 
150 MB 
150 MB 
150 MB 
150 MB 
150 MB 
150 MB 
File attachment size limit - OWA 6 
35 MB 
35 MB 
35 MB 
35 MB 
35 MB 
35 MB 
File attachment size limit - Outlook for Mac 
150 MB 
150 MB 
150 MB 
150 MB 
150 MB 
150 MB 
Multipart message limit 
250 parts 
250 parts 
250 parts 
250 parts 
250 parts 
250 parts 
Embedded message depth limit 
30 embedded messages 
30 embedded messages 
30 embedded messages 
30 embedded messages 
30 embedded messages 
30 embedded messages 

 Note

1 The default maximum message size for Office 365 mailboxes is 25 MB. Office 365 Administrators can specify a custom limit between 1 MB and 150 MB. However, the size of message you can send or receive also depends on what your email client or solution supports. For more information about customizing the maximum allowed message size for your organization, see Office 365 now supports larger email messages. 


2 You can send and receive up to 150 MB messages between Office 365 users (where the message never leaves the Office 365 datacenters). Messages that are routed outside of the Office 365 datacenters are subject to an additional 33% translation encoding increase, in which case the maximum message size is 112 MB


3 OWA accounts for the possibility that your message may be subject to the 33% encoding increase and restricts the size of message you can send to 25% less than the configured setting. For example, if you customize your settings for a 100 MB maximum message size, you can send messages no larger than 75 MB. 


4 The size of messages to be moved into Exchange Online are computed by Exchange Online. Versions of Exchange prior to Exchange Server 2013 may report a smaller item size. This limit applies to move based migrations using any supported Exchange Mailbox Replication Service. Other migration methods (Cutover, Staged, IMAP, PST) and other third party tools are limited by the general message size limit. 


5 For information about OME with new capabilities, see Set up new Office 365 Message Encryption capabilities built on top of Azure Information Protection
6 You cannot attach a single file that exceeds 35 MB. Additionally, you cannot attach files that collectively exceed 35MB. For example, if you attach one 34MB file, you can only attach an additional 1 MB file.

Message limits across standalone options

Feature 
Exchange Server 2013 
Exchange Online Plan 1 
Exchange Online Plan 2 
Exchange Online Kiosk 
Message size limit - Outlook 
10 MB4 
150 MB1, 2 
150 MB1, 2 
150 MB2 
Message size limit - OWA 
10 MB4 
112 MB1, 3 
112 MB1, 3 
150 MB1, 2 
Message size limit - Outlook for Mac 
10 MB4 
150 MB 
150 MB 
Message size limit - migration 
Not applicable 
150 MB 5 
150 MB 5 
150 MB 5 
Size limit for encrypted messages (for subscribers using Office 365 Message Encryption with new capabilities)6 
150 MB 
150 MB 
150 MB 
150 MB 
Size limit for encrypted messages (for subscribers using Office 365 Message Encryption legacy version)6 
25 MB 
25 MB 
25 MB 
25 MB 
Subject length limit 
255 characters 
255 characters 
255 characters 
255 characters 
File attachments limit 
1024 attachments4
250 attachments
250 attachments
250 attachments
File attachment size limit - Outlook 
35 MB4 
150 MB 
150 MB 
150 MB 
File attachment size limit - OWA 
35 MB4 
35 MB 
35 MB 
35 MB 
File attachment size limit - Outlook for Mac 
35 MB4 
150 MB 
150 MB 
35 MB 
Multipart message limit 
250 parts 
250 parts 
250 parts 
250 parts 
Embedded message depth limit 
30 embedded messages 
30 embedded messages 
30 embedded messages 
30 embedded messages 

 Note

1 Office 365 Administrators can specify a custom limit between 1 MB and 150 MB. However, the size of message you can send or receive also depends on what your email client or solution supports. For more information about customizing the maximum allowed message size for your organization, see Office 365 now supports larger email messages


2 You can send and receive up to 150 MB messages between Office 365 users (where the message never leaves the Office 365 datacenters). Messages that are routed outside of the Office 365 datacenters are subject to an additional 33% translation encoding increase, in which case the maximum message size is 112 MB. 


3 OWA accounts for the possibility that your message may be subject to the 33% encoding increase and restricts the size of message you can send to 25% less than the configured setting. For example, if you customize your settings for a 100 MB maximum message size, you can send messages no larger than 75 MB. 


4 This is the default limit for Exchange Server 2013 organizations. Administrators can change this value for their organization. 


5 The size of messages to be moved into Exchange Online are computed by Exchange Online. Versions of Exchange prior to Exchange Server 2013 may report a smaller item size. 


6 For information about OME with new capabilities, see Set up new Office 365 Message Encryption capabilities built on top of Azure Information Protection.

Receiving and sending limits

Receiving and sending limits are applied to combat spam and mass-mailing worms or viruses. These limits help to protect the health of our systems and keep our users safe.

Receiving limits

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 
Office 365 Business Essentials 
Office 365 Business Premium Office 
Office 365 Enterprise E1 
Office 365 Enterprise E3 
Office 365 Enterprise E5
Office 365 Enterprise F1 
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

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.

Note: 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.

 Note: 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.

Note: 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.

  • 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 overconsumption 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.

Sending limits across Office 365 options

Feature 
Office 365 Business Essentials 
Office 365 Business Premium 
Office 365 Enterprise E1 
Office 365 Enterprise E3
Office 365 Enterprise E5
Office 365 Enterprise F1 
Recipient rate limit 
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 limit 
500 recipients 
500 recipients 
500 recipients 
500 recipients 
500 recipients 
500 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 

Sending limits across standalone options

Feature 
Exchange Server 2013 
Exchange Online Plan 1 
Exchange Online Plan 2 
Exchange Online Kiosk 
Recipient rate limit 
No limit1 
10,000 recipients per day 
10,000 recipients per day 
10,000 recipients per day 
Recipient limit 
500 recipients1 
500 recipients 
500 recipients 
500 recipients 
Recipient proxy address limit 
400 
400 
400 
400 


 Note


1 This is the default limit for Exchange Server 2013 organizations. Administrators can change this value for their organization.





Keywords:Exchange, limits, Microsoft,   Doc ID:90064
Owner:Bruce P.Group:UW-Milwaukee Help Desk
Created:2019-02-28 09:14 CDTUpdated:2019-02-28 13:40 CDT
Sites:UW-Milwaukee Help Desk
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