sending > a few pics error message

Hello,

Whenever I try to send more than a few pictures via email, I get a similar response to thie one I just got from a Norton dialogue box:

 

"552 5.3.4 a message size of 20482 kilobites exceeds the sixe limit of 20480 kb computed for this transaction."

 

I guess Norton's firewall is not set-up to allow this size file to be sent as an attachment.

Can someone tell me how to correct this?

Thank you,

Robert