There might sometimes be sensitive information in an email thread that you'd like to exclude from future replies. For example, if you add a new recipient to the thread, and there's an earlier message you'd rather they didn't see.
SendBoard makes it super easy to toggle previous messages to be included/excluded from the replies you send.
Here's an example scenario where Jane is organising a surprise party for Bob.
The original email came in from Jane. When Mark replied, he did three things.
Added Bob as a contact on the reply.
Changed the subject of the email.
Clicked the checkbox on Jane's email to exclude it from his reply.
And as this conversation continues, any further replies sent out will automatically exclude the same message so that you don't need to carefully uncheck it each time.
Note that the ability to exclude past messages is only supported if you have chosen 'Show all messages (unless excluded)' as your message history format.