if the global is set to 20 but your 10MB file will not go out then you need to go into active directory users and computers, find your account. open it and go to I believe the Exchange General tab. that will show storage limits. if you have a custom setting on yours it will override the global. just checkmark use store defaults or change your custom setting. Messaage size limits can bet set on the mailbox or information store itself, you’ll have to check all of these places to see if the limit is on your end or somewhere else.
The other problem you may be having is your recipient may not be allowed to receive emails that large. And, if your forwarding through your ISPs SMTP server, via “Smart host” delivery instead of via DNS direct delivery, they may be blocking it as well. Can you tell us the error message you receive, that would help us understand your situation a little better.
I cheched AD user settings, for storage limits, it uses mailbox store defaults, for delivery restrictions, it also use defaults. The mailbox store has no limits setting. BTW, I use enterprise version. The SMTP vertual server has the same settings as global settings(allowed 20000KB message to be sent).