Can't Send an attachment over 10mb WHY!!??

Go to your Domain Controller and open ADSI Edit change the Connection Setting / Naming Context to Configuration.

For incoming e-mail:
CN=Configuration\CN=Services\CN=Microsoft Exchange\
CN=\CN=Administrative Groups\CN=Exchange Administrative Group (FYDIBOHF23SPDLT)\CN=Servers\CN='server'\CN=Protocols\CN=SMTP Receive Connectors msExchSmtpReceiveMaxMessageSize 10485760
Here is the first spot, notice it set to 10mb also notice its in Bytes!

Next spot:
For outgoing e-mail:
CN=Configuration\CN=Services\CN=Microsoft Exchange\
CN=\CN=Administrative Groups\CN=Exchange Administrative Group(FYDIBOHF23SPDLT)\CN=Routing Groups\CN=Routing Group (DWBGZMFD01QNBJR)\CN=Connections
delivContLength 10240
Here is the second spot, notice it set to 10mb also notice its in kilobytes

Next Spot:

CN=Configuration\CN=Services\CN=Microsoft Exchange\
CN=\CN=Global Settings\CN=Message Delivery <--Right Click Properties.

Look for the following:
delivContLength this value is in kilobytes change it
SubmissionContLength this value is in bytes change it
msExchRecipLimit this value is in kilobytes change it

Now we're on to Exchange 2007 settings: