Using the MaxReceiveSize and MaxSendSize you are able to limit the messagesize that is allowed to be transported. You generaly want to do this to block huge (in SMTP world) messages. These huge messages (when received and send) might require a huga ammount of system resources slowing down the overall performance or even make the outlook client go unresponsive.
An exchange administrator is able to alter these limits which are by default;
Exchange 2007 RTM (out of the box media)
send : Unlimited
Receive : Unlimited
maxRecipientEnvelopeLimit : Unlimited
Exchange 2007 SP1
send : 10MB
Receive : 10MB
maxRecipientEnvelopeLimit : 5000
Using the Exchange Management Powershell console you may use the following commands to alter these limits.
View the actual limits.
Alter the limits
Set-TransportConfig -MaxReceiveSize 20MB Set-TransportConfig -MaxSendSize 20MB
If you want the full documentation please review the following Microsoft Documentation…
Just a little reminder for me, there is a collection of registry keys in Exchange 2003 server that enables you to administer various OWA settings. One of the most anoying is the signature length that limits people to set the correct signature using the web-admin.
This is the path in the windows registry to alter these.
Level1FileTypes > String
Level1MIMETypes > String
Level2FileTypes > String
Level2MIMETypes > String
UseRegionalCharset > Dword ( 1 / 0 )
DisablePassword > Dword ( 1 / 0 )
KnownContentTypes > String
SignatureMaxLength > Dword
ALWAYS BACKUP YOUR REGISTRY KEYS BEFORE ALTERING THEM! USE THE REGEDIT EXPORT FUNCTION TO DO SO!
About the Levels the following is documented..
There are two levels of attachment security. Access to Level 1 files is blocked and can’t be changed. When you receive an attachment with a Level 2 file type, you will be prompted to save the file to your hard disk. If you use Microsoft Exchange Server, your system administrator can add and remove file types for both levels of e-mail security. If a file type is added to both levels, it will be treated as a Level 1 file type
Altering the SignatureMaxLength keep the following in mind;
The default SignatureMaxLength value is 4096 (4KB) and the maximum value is 16672 (16KB).
as documented here, http://forums.msexchange.org/Signature_Size_on_OWA/m_170055600/tm.htm
I didnt find the Microsoft documentation as of yet.