Managing Message Size Limits
Microsoft Exchange Server 2007 will reach end of support on April 11, 2017. To stay supported, you will need to upgrade. For more information, see Resources to help you upgrade your Office 2007 servers and clients.
Applies to: Exchange Server 2007, Exchange Server 2007 SP1, Exchange Server 2007 SP2, Exchange Server 2007 SP3
This topic describes the message size limits that you can apply to individual messages that traverse the Microsoft Exchange Server 2007 organization. You can restrict the total size of a message or the size of the individual components of a message, such as the message header, the message attachments, and the number of recipients. You can apply limits globally for the whole Exchange 2007 organization, or specifically for a particular connector or user object.
As you plan the message size limits for your Exchange 2007 organization, consider the following questions:
What size limits should I impose on all incoming messages?
What size limits should I impose on all outgoing messages?
Does my Exchange 2007 organization have a mailbox quota?
How do the message size limits that I have chosen relate to the mailbox quota size?
Are there special users in my Exchange 2007 organization who must send or receive messages that are larger that the specified allowed size?
Does my Exchange 2007 network topology include other messaging systems or distinctly separate business units that have different message size limits?
Types of Message Size Limits
The size limits that are available for individual messages can be divided into the following basic categories:
Message header size limits These limits apply to the total size of all message header fields that are present in a message. The size of the message body or attachments is not 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 character of text consumes 1 byte.
Note
Some third-party firewalls or proxy servers apply their own message header size limits. These third-party firewalls or proxy servers may have difficulty processing messages that contain attachment file names that are greater than 50 characters, or attachment file names that contain non-US-ASCII characters.
Message size limits These limits apply to the total size of a message. This includes the message header, the message body, and any attachments. Message size limits may be imposed on incoming messages or outgoing messages. For internal message flow, Exchange 2007 uses the custom
X-MS-Exchange-Organization-OriginalSize:message header to record the original message size of the message as it enters the Exchange 2007 organization. Whenever the message is checked against the specified message size limits, the lower value of the current message size or the original message size header is used. The size of the message can change because of content conversion, encoding, and agent processing.Attachment size limits These limits apply to the maximum allowed size of a single attachment within a message. The message may contain many attachments that greatly increase the overall size of the message. However, an attachment size limit would apply to the size of an individual attachment only.
Recipient limits These limits apply to the total number of message recipients. When a message is first composed, the recipients exist in the
To:,Cc:, andBcc:header fields. When the message is submitted for delivery, the message recipients are converted intoRCPT TO:entries in the message envelope. A distribution group is counted as a single recipient during message submission.
Scope of Limits
The scope of the limits that are available for individual messages can be divided into the following basic categories:
Organizational limits These limits apply to all Exchange 2007 servers that exist in the organization. The specified message limits apply to all Exchange 2007 servers that have the Hub Transport server role installed. On an Edge Transport server, the specified limits apply to the specific server.
Global limits These limits apply to all Exchange 2007 and Exchange Server 2003 servers that exist in the organization. The global message limits are stored in the Active Directory directory service.
In the release to manufacturing (RTM) version of Microsoft Exchange Server 2007, it is common for the organization limits and the global limits to conflict. When the organizational limits and the global message limits conflict, the lowest value takes precedence. In Exchange 2007 RTM, you must use Exchange System Manager on an Exchange 2003 server or the Active Directory Service Interfaces (ADSI) Edit tool to modify global message limits. For more information, see How to Modify Exchange 2003 Global Message Size Limits in Exchange 2007 RTM.
In Microsoft Exchange Server 2007 Service Pack 1 (SP1), the condition that cause the organization limits and the global limits to conflict has been eliminated. Changes that you make to the organizational limits are automatically copied to the corresponding global limits. In Exchange 2007 SP1, you can modify the organizational limits by using the Set-TransportConfig cmdlet in the Exchange Management Shell, or by configuring the Hub Transport server organization configuration properties in the Exchange Management Console.
Connector limits These limits apply to any messages that use the specified Send connector, Receive connector, or Foreign connector for message delivery. Connectors are defined on Hub Transport servers or Edge Transport servers.
In Exchange 2007 SP1, you can also set message size limits on the following types of connections:
Active Directory site links Hub Transport servers use Active Directory sites and the costs that are assigned to the Active Directory IP site links to determine the least cost routing path from each Hub Transport server in the organization to every other Hub Transport server in the organization. You can use the Set-AdSiteLink cmdlet to assign an Exchange-specific cost to the Active Directory IP site link. The Exchange-specific cost is a separate attribute that is used instead of the Active Directory-assigned cost to determine the least cost routing path. Any message size limits that are specified on an Active Directory site link don't affect the selection of the least cost routing path. Any messages that exceed the maximum message size limit on any Active Directory site link included in the least cost routing path won't be delivered, and will generate a delivery status notification (DSN) that has the value 5.3.4. For more information, about message routing in Exchange 2007, see Planning to Use Active Directory Sites for Routing Mail.
Routing group connectors A routing group connector is used to send and receive messages between Exchange 2007 Hub Transport servers and Exchange 2003 or Exchange 2000 bridgehead servers when the organization is running more than one version of Exchange Server. Any message size limits that are specified on a routing group connector don't affect the selection of the least cost routing path. Any messages that exceed the maximum message size limit on any routing group connector in the least cost routing path won't be delivered. They will generate a DSN that has the value 5.3.4. For more information about routing group connectors, see Message Routing in a Coexistence Environment.
For more information about message size limits on Active Directory site links and routing group connectors in Exchange 2007 SP1, see How to Configure Message Size Limits for Internal Routing.
Server limits These limits apply to a specific Hub Transport server or Edge Transport server. The specified message limits are not stored in the Active Directory directory service. You can set the specified message limits independently on each Hub Transport server or Edge Transport server.
Message size limits can apply to Microsoft Office Outlook Web Access on a Client Access server. For more information, see How to Manage Maximum Message Size in Outlook Web Access.
User limits These limits apply to a specific user object, such as a mailbox, contact, distribution group, or public folder.
Organizational Limits
The following table shows the organizational limits.
Organizational limits
| Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|
Set-TransportConfig |
MaxReceiveSize |
Unlimited |
10 MB |
Set-TransportConfig |
MaxSendSize |
Unlimited |
10 MB |
Set-TransportConfig |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Transport rule on a Hub Transport server that applies to all Hub Transport servers in the organization. |
AttachmentSizeOver |
Not configured |
Not configured |
Global Limits
The following table shows the global limits.
Global limits
| Source | Property | Default value |
|---|---|---|
Active Directory |
|
10240 KB (10 MB) |
Active Directory |
|
10240 KB (10 MB) |
Active Directory |
|
5000 |
Conditions That Affect the Initial Values of Global Limits in Exchange 2007 RTM
In Exchange 2007 RTM, the initial values of the global limits differ from the default values only when the organization was upgraded from Exchange 2003, and a numeric value was specified for Incoming message size, Outgoing message size, or Maximum number of recipients. The numeric value is preserved after the upgrade to Exchange 2007 RTM.
In Exchange 2007 RTM, any changes that you make to an organizational limit by using the Set-TransportConfig cmdlet are never copied to the corresponding global limit. In Exchange 2007 RTM, you must use Exchange System Manager on an Exchange 2003 server or the ADSI Edit tool to modify global message limits. For more information, see How to Modify Exchange 2003 Global Message Size Limits in Exchange 2007 RTM. We recommend that you set the global limits and the corresponding organization limits to the same values.
Conditions That Affect the Initial Values of Global Limits in Exchange 2007 SP1
The following list describes the conditions that cause the initial values of the global limits to differ from the default values in Exchange 2007 SP1:
The existing numeric values of delivContLength, submissionContLength, or msExchRecipLimit are preserved for the following circumstances:
The organization was upgraded from Exchange 2007 RTM and the corresponding organizational limit values that are specified by the MaxReceiveSize parameter, the MaxSendSize parameter, or the MaxRecipientEnvelopeLimit parameter on the Set-TransportConfig cmdlet were set to
Unlimited.The organization was upgraded from Exchange 2003, and a numeric value was specified for Incoming message size, Outgoing message size, or Maximum number of recipients.
The values of delivContLength, submissionContLength, or msExchRecipLimit are changed to match the values of the corresponding organizational limits that are specified by the MaxReceiveSize parameter, the MaxSendSize parameter, or the MaxRecipientEnvelopeLimit parameter on the Set-TransportConfig cmdlet when all the following conditions are true:
The organization was upgraded from Exchange 2007 RTM to Exchange 2007 SP1.
A numeric value was specified for delivContLength, submissionContLength, or msExchRecipLimit.
A different numeric value was specified for the corresponding organizational limit in the MaxReceiveSize parameter, the MaxSendSize parameter, or the MaxRecipientEnvelopeLimit parameter.
In Exchange 2007 SP1, you shouldn't modify the global limits directly. In Exchange 2007 SP1, if you set a global limit to a different value than the corresponding organizational limit, you will generate event log errors. When you want to modify the organizational limits or the global limits in Exchange 2007 SP1, you should use the Set-TransportConfig cmdlet in the Exchange Management Shell or the Hub Transport organization configuration properties in the Exchange Management Console. When you modify an organizational limit in Exchange 2007 SP1, the new value is automatically copied to the corresponding global limit.
Connector Limits
The following table shows the connector limits.
Connector limits
| Source | Parameter | Version | Default value |
|---|---|---|---|
Set-ForeignConnector |
MaxMessageSize |
Exchange 2007 RTM and Exchange 2007 SP1 |
Unlimited |
Set-ReceiveConnector |
MaxHeaderSize |
Exchange 2007 RTM and Exchange 2007 SP1 |
64 KB |
Set-ReceiveConnector |
MaxMessageSize |
Exchange 2007 RTM and Exchange 2007 SP1 |
10 MB |
Set-ReceiveConnector |
MaxRecipientsPerMessage |
Exchange 2007 RTM and Exchange 2007 SP1 |
200 |
Set-SendConnector |
MaxMessageSize |
Exchange 2007 RTM and Exchange 2007 SP1 |
10 MB |
Set-AdSiteLink |
MaxMessageSize |
Exchange 2007 SP1 |
Unlimited |
Set-RoutingGroupConnector |
MaxMessageSize |
Exchange 2007 SP1 |
Unlimited |
Server Limits
The following table shows the server limits.
Server limits
| Source | Parameter | Default value |
|---|---|---|
Transport rule on an Edge Transport server that only applies to the specific server |
AttachmentSizeOver |
Not configured |
Set-TransportServer on a Hub Transport server or Edge Transport server |
PickupDirectoryMaxHeaderSize |
64 KB |
Set-TransportServer on a Hub Transport server or Edge Transport server |
PickupDirectoryMaxRecipientsPerMessage |
100 |
Outlook Web Access Web.config file on a Client Access server |
maxRequestLength |
30000 KB |
User Limits
The following table shows the user limits.
User limits
| Source | Parameter | Default value |
|---|---|---|
Set-DistributionGroup |
MaxReceiveSize MaxSendSize |
Unlimited |
Set-DynamicDistribution Group |
MaxReceiveSize MaxSendSize |
Unlimited |
Set-Mailbox |
MaxReceiveSize MaxSendSize RecipientLimits |
Unlimited |
Set-MailContact |
MaxReceiveSize MaxSendSize MaxRecipientPerMessage |
Unlimited |
Set-MailPublicFolder |
MaxReceiveSize MaxSendSize |
Unlimited |
Set-MailUser |
MaxReceiveSize MaxSendSize RecipientLimits |
Unlimited |
Order of Precedence for Message Size Limits
You can set different message size limits for the same message component, such as the maximum message size, at different levels in the Exchange organization. When different message size limits are applied to the same message component, Exchange 2007 uses an order of precedence to enforce the message size limit that is imposed on the same message component.
For example, the recipient will receive a message that was sent by a particular sender if the following conditions are true:
An organization-wide send and receive message size limit of 10 MB is imposed on the Exchange 2007 organization.
A particular sender's mailbox has a send message size limit of 20 MB.
The recipient's mailbox has a receive message size limit of 20 MB.
Generally, it is better to maximize the restrictiveness of your message size limits. You should base any exceptions on a proven need to exceed the established size limits, and you should put those limits as close as possible to the objects that must exceed the established size limits. This strategy helps make sure that messages in the transport pipeline are rejected as early as possible if they violate message size limits. It is a waste of system resources to set a high message size limit at the Exchange organization level, allow a message to enter the Exchange organization, and then reject the message at the last stage of delivery because of a violation of a message size limit.
Message Size Limits in Message Delivery Scenarios
The tables in the following sections present scenarios that demonstrate how you can apply various message size limits in Exchange 2007 RTM and in Exchange 2007 SP1.
Internet to Edge Transport Server
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Edge Transport server Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
Note
The MaxReceiveSize and MaxEnvelopeReceiveLimit parameters are not used on an Edge Transport server. Use the message size limits on the Send and Receive connectors that are configured on an Edge Transport server to control the size of messages processed by the server.
Anonymous senders are always subject to the message size limits on the Receive connector that accepts messages from the Internet.
The default value of the MaxRecipientsPerMessage setting on the Receive connector is 200 recipients. If the number of recipients is exceeded for an anonymous sender, the message is accepted for the first 200 recipients. Most SMTP messaging servers will detect that a recipient limit is in effect. The SMTP messaging server will continue to resend the message in groups of 200 recipients until the message is delivered to all recipients.
Edge Transport Server to Hub Transport Server
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Connector on Edge Transport server |
Send connector |
MaxMessageSize |
10 MB |
10 MB |
Connector on Hub Transport server |
Receive connector |
MaxRecipientsPerMessage |
200 |
200 |
Connector on Hub Transport server |
Receive connector |
MaxMessageSize |
10 MB |
10 MB |
Connector on Hub Transport server |
Receive connector |
MaxHeaderSize |
64 KB |
64 KB |
Recipient |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxReceiveSize |
Unlimited |
Unlimited |
All Hub Transport servers in the organization |
Transport rule |
AttachmentSizeOver |
Not configured |
Not configured |
Organization |
Transport configuration |
MaxReceiveSize |
Unlimited |
10 MB |
Organization |
Transport configuration |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
An X-header that is named X-MS-Exchange-Organization-OriginalSize: is inserted into the message header. Any Hub Transport servers that are involved in the future delivery of the message will use this value for the message size. Conversion encoding and agent processing can increase the size of the message as it flows through the Exchange organization.
Hub Transport Server to Hub Transport Server in the Same Active Directory Forest
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Sender |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxSendSize |
Unlimited |
Unlimited |
Recipient |
Mail contact |
MaxRecipientPerMessage |
Unlimited |
Unlimited |
Recipient |
Mailbox Mail user |
RecipientLimits |
Unlimited |
Unlimited |
Recipient |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxReceiveSize |
Unlimited |
Unlimited |
All Hub Transport servers in the organization |
Transport rule |
AttachmentSizeOver |
Not configured |
Not configured |
Organization |
Transport configuration |
MaxReceiveSize |
Unlimited |
10 MB |
Organization |
Transport configuration |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
In Exchange 2007 SP1, you can set a maximum message size limit on an Active Directory site link or a routing group connector. For more information, see How to Configure Message Size Limits for Internal Routing.
Hub Transport Server to Hub Transport Server in Different Active Directory Forests
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Sender |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxSendSize |
Unlimited |
Unlimited |
Connector |
Send connector |
MaxMessageSize |
10 MB |
10 MB |
Connector |
Receive connector |
MaxRecipientsPerMessage |
200 |
200 |
Connector |
Receive connector |
MaxMessageSize |
10 MB |
10 MB |
Connector |
Receive connector |
MaxHeaderSize |
64 KB |
64 KB |
Recipient |
Mail contact |
MaxRecipientPerMessage |
Unlimited |
Unlimited |
Recipient |
Mailbox Mail user |
RecipientLimits |
Unlimited |
Unlimited |
Recipient |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxReceiveSize |
Unlimited |
Unlimited |
All Hub Transport servers in the destination organization |
Transport rule |
AttachmentSizeOver |
Not configured |
Not configured |
Destination Organization |
Transport configuration |
MaxReceiveSize |
Unlimited |
10 MB |
Destination Organization |
Transport configuration |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Destination Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
If a specific Receive connector is configured in the destination Active Directory forest to accept messages from the source Active Directory forest, that specific Receive connector should have the ExchangeServers permission group and the ExernalAuthoratative authentication method assigned. This permission group contains the Ms-Exch-Bypass-Message-Size-Limit permission that allows messages to flow through the Receive connector without checking the message size. The message is still be subject to organization, transport server, sender, and recipient limits that are defined in the destination Active Directory forest.
For more information, see Configuring Cross-Forest Connectors.
Mailbox Server to Hub Transport Server
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Sender |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxSendSize |
Unlimited |
Unlimited |
Recipient |
Mail contact |
MaxRecipientPerMessage |
Unlimited |
Unlimited |
Recipient |
Mailbox Mail user |
RecipientLimits |
Unlimited |
Unlimited |
Recipient |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxReceiveSize |
Unlimited |
Unlimited |
All Hub Transport servers in the organization |
Transport rule |
AttachmentSizeOver |
Not configured |
Not configured |
Organization |
Transport configuration |
MaxReceiveSize |
Unlimited |
10 MB |
Organization |
Transport configuration |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
Submission by a Foreign Connector
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Sender |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxSendSize |
Unlimited |
Unlimited |
All Hub Transport servers in the organization |
Transport rule |
AttachmentSizeOver |
Not configured |
Not configured |
Connector |
Foreign connector |
MaxMessageSize |
10 MB |
10 MB |
Organization |
Transport configuration |
MaxReceiveSize |
Unlimited |
10 MB |
Organization |
Transport configuration |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
Submission by the Pickup Directory
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Server |
Transport server |
PickupDirectoryMaxHeaderSize |
64 KB |
64 KB |
Server |
Transport server |
PickupDirectoryMaxRecipientsPerMessage |
100 |
100 |
Server |
Transport rule |
AttachmentSizeOver |
Not configured |
Not configured |
Organization |
Transport configuration |
MaxReceiveSize |
Unlimited |
10 MB |
Organization |
Transport configuration |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
Submission by the Replay Directory
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Server |
Transport Rule |
AttachmentSizeOver |
Not configured |
Not configured |
Organization |
Transport configuration |
MaxReceiveSize |
Unlimited |
10 MB |
Organization |
Transport configuration |
MaxRecipientEnvelopeLimit |
Unlimited |
5000 |
Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
Hub Transport Server to Edge Transport Server
| Scope | Source | Parameter | Default value in Exchange 2007 RTM and Exchange 2007 SP1 |
|---|---|---|---|
Sender |
Distribution group Dynamic distribution group Mailbox Mail contact Mail-enabled public folder Mail user |
MaxSendSize |
Unlimited |
Connector on Hub Transport server |
Send connector |
MaxMessageSize |
10 MB |
Connector on Edge Transport server |
Receive connector |
MaxRecipientsPerMessage |
200 |
Connector on Edge Transport server |
Receive connector |
MaxMessageSize |
10 MB |
Connector on Edge Transport server |
Receive connector |
MaxHeaderSize |
64 KB |
Edge Transport Server to the Internet
| Scope | Source | Parameter | Default value in Exchange 2007 RTM | Default value in Exchange 2007 SP1 |
|---|---|---|---|---|
Edge Transport server Organization |
Transport configuration |
MaxSendSize |
Unlimited |
10 MB |
Note
: The following parameters are not used on an Edge Transport server. Use the message size limits on the Send and Receive connectors that are configured on an Edge Transport server to control the size of messages processed by the server.
•MaxReceiveSize
•MaxEnvelopeReceiveLimit
Messages That Are Generated by Transport Servers
The following list shows the types of messages that are generated by a Hub Transport server or an Edge Transport server and exempted from all message size limits:
System messages
Agent-generated message
Delivery status notification (DSN) messages
Journal report messages
Quarantined messages
However, these messages are still subject to the organizational MaxRecipientEnvelopeLimit that is configured by using the Set-TransportConfig cmdlet in the Exchange Management Shell.
Differences in Message Size Limits Between Exchange Server 2003 to Exchange 2007
The primary difference in message size limits between Microsoft Exchange Server 2003 and Exchange Server 2007 is in the handling of recipient limits. Exchange 2007 treats a distribution group as one recipient. Exchange 2003 treats each member of the expanded distribution list as one recipient. This change was implemented to avoid the partial message delivery scenarios that may occur in Exchange 2003.
Partial message delivery occurs in Exchange 2003 if the number of individual recipients and the recipients that are contained within the distribution list exceeds the specified recipient limit. The total number of message recipients isn't known until after distribution list expansion. Message delivery occurs as the distribution list is expanded until the number of recipients reaches the specified limit. The remaining recipients don't receive the message, but at least the sender receives a non-delivery report (NDR) for each unsuccessful delivery. However, if delivery failure reporting is disabled for the distribution list, the remaining recipients wouldn't receive the message, and the sender would not know who didn't receive the message.
For More Information
For more information, see the following topics: