Exchange Server 2013 email size restriction

[Xavier Mustin]

Exchange Server 2013 email size restriction

Email size in Exchange server plays an important role for the organization since it acts important factor for bandwidth, storage limit, email queue, CPU utilization and mailbox size. The below article provide deeper stuff on how email size restriction plays in the Exchange server 2013.

The email message size value you are trying to configure should be 33% larger than the actual message sizes. For example if you want to allow 30 MB email size then the message size parameter should be 43 MB value. The reason behind is it uses Base64 encoding which increase the message size to 33% of the real message size.

The email size restriction for user mailbox will be applied in the following order

1. Global Transport configuration settings
2. Send connector size restriction
3. Receive connector size restriction
4. In the user mailbox properties of send and receive size limit

It’s also controlled in the configuration file of Exchange Server based upon the application

1. Exchange Web Service (EWS)
2. Outlook Web Access (OWA)
3. ActiveSync

Thumb Rule: If the upper order is more restrictive, then this will override the below order. For example if the Global Transport setting send receive size is 10 MB and Send connector size is 100MB. The user will not able to send more email more than 10 MB size.

Now let us understand in detail on how each component works

• Global Transport configuration settings

To verify global transport settings all Hub Transport servers in the Exchange Organization. The default of send and receive size is 10 MB. Complete global transport configuration setting can be displayed used the command

Get-TransportConfig | fl

To check only the send and receive size of email

Get-TransportConfig | ft MaxSendSize, MaxReceiveSize

For example if you want to modify the sending and receiving email message size to 100 MB in the global Tranport configuration

Set-TransportConfig –MaxSendSize 20MB –MaxReceiveSize 100MB

• Send connector size restriction

Send connector are used to send emails out of the exchange organization and the default size is 10 MB. To verify and modify the send connector size

Get-SendConnector | ft name, MaxMessageSize

Set-SendConnector <Connector Name> –MaxMessageSize 50MB

• Receive connector size restriction

Receive connector are used to receive emails from the internet or application and the default size is 10 MB. To verify and modify the receive connector size

Get-ReceiveConnector | ft name, MaxMessageSize

Set-ReceiveConnector <Connector Name> –MaxMessageSize 50MB

• In the user mailbox properties of send and receive size limit

The send and receive email message size can be granular controlled in the user mailbox properties. To verify the and modify the size

Get-mailbox | ft Name, MaxSendSize, MaxReceiveSize

Set-Mailbox “test” –MaxSendSize 20MB –MaxReceiveSize 20MB

Exchange Server Configuration File – Email Size Restriction

• 1. Outlook Web Access

When email sent over the Outlook Web Access the email size is also verified in the web config file located in %ExchangeInstallPath%ClientAccess\Owa\web.config

Default Email message size in OWA:

maxAllowedContentLength=”35000000″ (value in bytes) = Approx 33 MB

maxReceivedMessageSize=”35000000″ (value in bytes) = Approx 33 MB

maxRequestLength=”35000″ (value in kilobytes) = Approx 34 MB

You can change this value to whatever size you need.

• 2. Exchange Web Services (EWS)

Just like OWA, when email is sent using the EWS application (Mac Outlook, Entourage) the message size is justified with the parameter value located in the fileExchangeInstallPath%ClientAccess\exchweb\ews\web.config

Default Email message size in EWS:

maxAllowedContentLength=”67108864″ (value in bytes) = Approx 64 MB

maxReceivedMessageSize=”67108864″ (value in bytes) = Approx 64 MB

You can change this value to whatever size you need.

• 3. ActiveSync

When email is sent using the ActiveSync handheld device the message size is justified with the value located in the file %ExchangeInstallPath%ClientAccess\Sync\web.config

Default Email message size in Activesync:

<add key=”MaxDocumentDataSize” value=”10240000″> (value in bytes) Approx 9.7 MB

maxRequestLength=”10240″ (value in kilobytes ) = Approx 10 MB

Error Message and NDR

There are various error message which is listed below will occur if the value is not configured as per the above rule.

Error 1:

The following recipient(s) could not be reached:

raji@mail.com on 01/15/2014 3:54 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.

<mail.com #5.2.3 smtp;450 5.2.3 Msg Size greater than allowed by Remote Host>

Error 2:

The following recipient(s) could not be reached

raji@mail.com on 01/15/2014 3:54 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.

<mail.com #5.2.3 smtp;550 5.2.3 RESOLVER.RST.SendSizeLimit; message too large for this sender>

Error 3:

Delivery has failed to these recipients or distribution lists:

administrator@mail.com
This message exceeds the maximum message size allowed. Microsoft Exchange will not try to redeliver this message for you. Please make the message smaller — by removing attachments, for example — and try sending it again, or provide the following diagnostic text to your system administrator.

Diagnostic information for administrators:
Generating server: MBX01.mail.com
administrator@mail.com
#550 5.2.3 RESOLVER.RST.SendSizeLimit; message too large for this sender ##

Error 4

OWA Error – The request filter module is configured to deny a request that exceeds the request content length”

Error 5

EWS Error – Email is goes in drafts or never leaves the outbox and the client receives an “exceeded the size limit”