Hosted Microsoft® Exchange®

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 fall into one of the following categories:

Exchange Online Limits

Address list limit 1000
Offline address book (OAB) limit 250
Address book policies (ABP) limit 250
Global address lists limit 250

Mailbox folder limits across Hosted Exchange options

Maximum number of messages per mailbox folder 1 million
Warning for number of messages per mailbox folder 900,000
Maximum number of messages per folder in the Recoverable Items folder 3 million
Warning for number of messages per folder in the Recoverable Items folder 2.75 million
Maximum number of subfolders per mailbox folder 10,000
Warning for number of subfolders per mailbox folder 900
Maximum folder hierarchy depth 300
Warning for folder hierarchy depth 250
Maximum number of public folders 100,000
Maximum number of subfolders per public folder 1,000
Warning for number of subfolders per public folder 900

Message limits

Message size limit – Outlook 50MB
Message size limit – OWA 50MB
Message size limit – Outlook for Mac 35 MB
Message size limit – migration 50MB
Subject length limit 255 characters
File attachments limit 250 attachments
File attachment size limit – Outlook 50MB
File attachment size limit – OWA 25 MB
File attachment size limit – Outlook for Mac 35 MB
Multipart message limit 250 parts
Embedded message depth limit 30 embedded messages

Recipient and sender limits

Recipient rate limit 10,000 recipients per day
Recipient limit 500 recipients

Retention limits

Deleted Items folder retention period No limit
Retention period for items removed from the Deleted Items folder 14 days
Junk Email folder retention period 30 days

Distribution group limits

Maximum number of distribution group members 100,000 members
Limit sending messages to large distribution group 5,000 or more members
Maximum message size for large distribution groups 10 MB

Exchange ActiveSync limits

Exchange ActiveSync device limit 100
Exchange ActiveSync device deletion limit 20
Exchange ActiveSync file attachment limit 25 MB