How to Set Size Limits for Messages

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It is possible to set size limits for messages in your Exchange organization on several objects in Exchange System Manager. This article will show you where you can set these limits and how they interact.

You can set message limits on the following objects:

  • Global settings
  • System Policy
  • Individual mailbox
  • Individual message limit
  • Distribution list
  • Public folder
  • Connector
  • Virtual SMTP Server

Global settings

Exchange 2003 sets a default limit for incoming messages into your Exchange organization and a limit for outgoing messages. You can set these limits in Exchange System Manager under Global SettingsMessage Delivery – right click Properties and select the Defaults register.

Figure 1: Global message limits

If you have configured a size limit on either the Send or Receive sizes in global settings, the more restrictive limit applies to both incoming and outgoing e-mail messages.

System policy limits

A system policy is a collection of configuration settings that you apply to one or more servers, mailbox stores, or public folder stores. For example, to enable storage limits for your mailbox stores, you can define a single policy and apply them to all mailbox stores in your administrative group.

The system policies that you create for an administrative group typically apply to objects within that group. For more information about System policies read the following article.

Figure 2: System Policy example

Mailbox limit

You can set message limits for mailboxes at the mailbox store. Every mailbox in this mailbox store inherits these limits. For more information about mailbox management and how to set limits, read the following article.

It is possible to set a message size limit for individual mailboxes. Each default mailbox inherits the message size limit from the mailbox store.

To set an individual mailbox limit, click Start  RunDSA.MSC, select the user and navigate to Exchange General and click Storage Limits.

Figure 3: Individual mailbox limits

Message size limit

If you wish to set an individual send/receive message limit, select the user account and click Delivery Restrictions and set the maxium message size.

Figure 4: Individual message size limits

Distribution list

It is also possible to limit the message size of message send to distribution lists. To activate a message size limit for distribution lists, click StartRunDSA.MSC, select the distribution list, click Exchange General and set the desired limit.

Figure 5: Limits for distribution lists

Public folder

You can also set a storage limit for public folders. You can set storage limits at the public folder store or individual public folders. For more information about public folders read the following article.

Figure 6: Storage limits for public folders

Connector limits

Connectors in Exchange Server 2003 are used to send messages to foreign mail systems. It is possible to set message size limits at individual connectors. Start Exchange System manager, navigate to the connector, select Content Restrictions and set the allowed Size. For more information about connectors (especially the SMTP connector) read the following article.

Figure 7: Message size limit for an SMTP connector

Virtual SMTP server

The last place where you can limit the message size is the virtual SMTP server.

Settings that you define here are valid for every message sent through this Virtual Server. Note that for example the public folder replication uses this Virtual Server. I recommend using a message limit at the virtual SMTP server only for explicit SMTP relay server or other than the default Virtual SMTP server.

Figure 8: Message limits at the SMTP Virtual Server limit

Effective Limits

As you have seen in this article, it is possible to set message size limits for a variety of objects in Exchange 2003 and the question is now – What message restriction is most effective?

The easiest way to explain what message restriction is effective is to show through an example:

  • The global setting is set to 10 MB.
  • The Exchange SMTP connector limit is set to 4.5 MB.
  • The SMTP Virtual Server limit is set to 4 MB.
  • The user mailbox setting limit is set to 3 MB.

Because of these settings, users in the Exchange 2003 organization can send and receive messages that are a maximum of 10 MB. Users can send messages through the SMTP connector with a maximum size of 4.5 MB. All mails that pass through the SMTP Virtual Server (Send/receive) are limited to 4 MB. The individual user, whose mailbox setting is 3 MB, is also limited to sending and receiving messages that are a maximum of 3 MB.

Please keep in mind that messages sent through SMTP could grow about 10-20 percent because of format conversion (MIME and UUEncode).

Sample NDR message

Users sending larger messages than the specified limit on the destination mailbox will get the following message:

Subject: Message to Sean
Sent: 5/12/2005 5:40 PM
The following recipient(s) could not be reached:
Sean on 5/12/2005 5:36 PM
This message is larger than the current system limit or the recipient’s mailbox is full. Create a shorter message body or remove attachments and try sending it again.
<london.nwtraders.msft #5.2.3>


It is possible to set mailbox size limits on several objects in Exchange Server 2003. You should know where to set this limits and how they interact.

Related Links

How to set size limits for messages in Exchange Server;en-us;322679

HOW TO: Use System Policies to Configure Mailbox Storage Limits in Exchange Server 2003;en-us;822938

HOW TO: Configure Storage Limits on Public Folders in Exchange 2003;en-us;823144

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1 thought on “How to Set Size Limits for Messages”

  1. Michael Aguirre

    The Effective Limits section example makes no sense. The example given claims conflicting conclusions. You say that users can send emails 10mb size, but don’t explain that all the other limits will stop them from sending/receiving anything bigger than 3mb. This is confusing as i came in to see how to limit qty of recipients to external addresses, but keep internal limits higher.

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