You are a hero.

One question, does the application only send SMS received since activated, or can it send all existing SMS in Conversations?

Second option would be great as it would allow us to make a full backup of the received SMS.

Another question, could it be possible to define the subject of the emailed messages with tags such as "SMS from [CONTACT]" ?. This way it would be easy to create filters in GMail to arrange the messages.

I can't count all the great applications I have in my phone developed by you...