Microsoft Office 365 Message limits

Microsoft Office 365 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.

    NoteNote:
    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.
  • 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.

    NoteNote:
    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.

 

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

NoteNote:
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. 
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.

 

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

NoteNote:
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.

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