For e-organizer - In the Organizer listing is E-Mail Letter You can edit that to your hearts desire. 

For Link - When you Invite there is a Dear [CLIENTNAME], followed by some text that you can edit to your hearts desire. 

If you send something from the Client Screen, you are presented with an e-mail and attachment. You can edit the text of that e-mail to you hearts desire before you click send. 

I know of no automated message that Lacerte sends out, only messages YOU send out through Lacerte. Please add a comment if I am missing something.