I think that is the same one my GM used. Initially, she was spamming people. Several of us brought up the issues with that and then made her roll a low level unguilded toon to see it first hand. She agreed how annoying it was and started playing with settings.
Now, I don't know for sure if she continued to use that addon or switched but I believe she was still using that addon. She eventually set it up so that it did not send any message automatically. Instead, it provided her with a list. She could then choose which players to send the message to. If they replied negatively, she placed them in a black list so they would not come up again.
Obviously, she was also only sending a message and not an invite until she talked to them at that point.
As to what message to send, just be honest. Tell them what your vision of the guild is and it's goal. It's likely to be slow going since it doesn't sound like you are working toward being a goal oriented guild and you are not high enough yet to have the leveling bonuses but every new guild fights that same problem.
Last edited by sifuedition; 01-09-2013 at 06:08 AM.
"he doens't need healing, he doesn't need healing, he doesn't nee-WHAOSHIT!wtf was that man!". Please stop leaning on TDR. -Teng