So, I just ran into this problem again today. I know how to solve it, but when I just want to sent out a dozen statements it is not convenient. 

If you change text in the email send box, it will change the text in the FIRST email message, then all the others will have the default message - a pretty stupid way to have this work. To fix it you must:

-Log in as the Administrator 

-Go to Edit>Preferences>Send Forms 

-Go to the Company Preferences tab  here you can select one of possibly several basic messages to send by setting them as "Current Default". Or, you can create a new message by selecting "add a template". You create, name, and save the message then select it as default. 

Then when you go to send your dozen email messages, they will all get the selected message. 

Does this suck? Absolutely. It is the stupidest way to change an outgoing message I can imagine. It requires that you remember to do all this BEFORE you start your emailing and it requires that you logout, login, logout and log back in again before you sent your messages. It is IRRESPONSIBLE that Intuit would allow a simple task, like sending a few emails, to be so complicated.