Open ESM ( Exchange System Manager )  > Expand Global Settings > Right click Message Delivery then click Properties.
Click on Defaults TAB , set your Message size limit then click OK to accept changes .

Had few errors with exchange server lately , after examing the Event viewer log i got the following errors :

Event Type: Error
Event Source: MSExchangeDSAccess
Event Category: Topology
Event ID: 2103
Date: 5/2/2007
Time: 8:49:47 AM
User: N/A
Computer: exchange server
Description:
Process MAD.EXE (PID=1792). All Global Catalog Servers in use are not responding:
yourserver.domain.com ( Domain controller )
Event Type: Error
Event Source: MSExchangeSA
Event Category: RFR Interface
Event ID: 9074
Date: 5/2/2007
Time: 8:49:04 AM
User: N/A
Computer: exchange server
Description:
The Directory Service Referral interface failed to [...]

It was a great day to whoop somebody’s ass yesterday !!
Our Main Domain Controller that has all the FSMO Roles assigned to it & the [global catalog] , decided that Moody [me] has to stay late @ work and crashed it self ….
I tried to Boot it up but it didn’t want to … Hard [...]