Tuesday, July 16, 2013

Setting and checking message size limits on Exchange Server 2010

source: http://eightwone.com/2010/09/29/exchange-message-size-limits/


Exchange Message Size Limits

While traveling trough your Exchange organization or beyond, e-mail messages may be imposed to all sorts of limitations. One of these limits is the message size limit, which can be set on the following levels:
  • Organizational Level
  • Send Connector
  • Receive Connector
  • AD Site Links
  • Routing Group Connectors
  • Individual
The path evaluated is as follows: User Send Limit > Receive Connector > Organization Checks > Send Connector > User Receive Limit

In general, the lowest size limit on an e-mail route determines if a message can be successfully transported from sender to the recipient. Exception is the individual setting which can override the other settings for internal messages. Strategy is to define limits where appropriate and as soon as possible. It’s a waste of resources to accept a message, send it throughout the organization via several hops, to finally reject the message because the recipient has a maximum receive size limit.

Organizational Level

The message size limits on the organization level can be set through the Exchange Management Console via Organization Configuration > Hub Transport > Global Settings by opening the Properties of Transport Settings:


TransportSettings

Of course, you can also view the settings using the Exchange Management Shell using Get-TransportConfig, e.g.


TransportSettings-EMS
As you can see, the default value in Exchange 2010 is 10240 (10 MB) for both receive as well as send message sizes. If you require a higher value, for example to enable people to send and receive larger attachments, you can use the EMC or Set-TransportConfig:

Set-TransportConfig –MaxReceiveSize 25MB –MaxSendSize 25MB

As you might expect, MaxReceiveSize applies to receive connectors, MaxSendSize applies to send connectors. Valid range for this setting is anywhere in the range between 64KB and 2GB or Unlimited. When set to Unlimited (which once was the default values in Exchange 2007 RTM), no limit will be imposed. I don’t recommend using Unlimited since it can lead to service disruption caused by processing large messages.

Send Connector

The message size limits on a send connector can be set through the Exchange Management Console via Organization Configuration > Hub Transport > Send Connectors by opening the Properties of the Send Connector:

SendConnector-EMC 

You can also use Get-SendConnector to view the setting:

SendConnector


The default maximum sending message size for Exchange 2007/2010 send connectors is 10 MB. If you want to be able to send larger messages over this send connector, you can use the EMC or Set-SendConnector:

Set-SendConnector –Identity Internet –MaxMessageSize 25MB

Valid range for this setting is anywhere in the range between 64KB and 2GB or Unlimited.

Receive Connector

The message size limits on a send connector can be set through the Exchange Management Console via Server Configuration > Hub Transport by opening the Properties of the Receive Connector in the Receive Connectors pane:

ReceiveConnector-EMC

You can also use Get-ReceiveConnector:

ReceiveConnector
The default maximum receiving message size for receiving messages for Exchange 2007/2010 receive connectors is 10 MB. If you want to be able to receive larger messages over this receive connector, you can use the EMC or Set-ReceiveConnector:

Set-ReceiveConnector –Identity “MAIL1\Default MAIL1” –MaxMessageSize 25MB

Valid range for this setting is anywhere in the range between 64KB and 2GB or Unlimited.


AD Site Link

Messages travelling between Hub Transport servers are subject to AD site link limits. By default site links have no message size limit. You can view AD site link settings using Get-AdSiteLink or use Set-AdSiteLink to configure MaximumMessageSize when required.


ADSiteLink
Note that Hub Transport servers use least cost routing to route messages. When a message exceeds a site link limit, the message will not be delivered. Hub Transport servers will not try to deliver the message using a different route.

Routing Group Connectors

In a co-existence scenario you might have routing group connectors connecting Exchange 2007/2010 to an Exchange 2003 environment. Routing group connectors have no maximum message size limit by default.
To inspect a routing group connector maximum message size settings, use Get-RoutingGroupConnector:

Get-RoutingGroupConnector <ConnectorID> | FL Name, *Max*

To configure a maximum message size limit on a RGC use Set-RoutingGroupConnector:

Set-RoutingGroupConnector <ConnectorID> -MaxMessageSize 25Mb
Individual

You can create exceptions for the MaxReceiveSize and MaxSendSize values for mailbox users, mail-enabled contacts and distribution groups. By default no limits are imposed (i.e. Unlimited). To inspect the settings for a mailbox user, navigate to Recipient Configuration > Mailbox and open the Properties of the User. Activate tab Mail Flow Settings and open the Properties of the Message Size Restrictions settings:

UserMessageSizeSettings

or use the related cmdlet, e.g. Set-Mailbox UserID –MaxSendSize 1GB –MaxReceiveSize 1GB:

UserMessageSizeSettings-EMS

If you set an individual maximum send or receive size setting higher than the organization or connector limits, the individual setting will override those limits when the message is send internally, e.g the recipient resides in the same organization. This way you can create exceptions for certain individuals which require a higher message size limit.

source: http://eightwone.com/2010/09/29/exchange-message-size-limits/

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