Now this has happened to me a lot of times - After we get a new signup here, the forum software automatically sends them a welcome email.

Till now I've been using this generic email text -
Voila! I've had so many replies to this welcome email and nearly all of them went like this -

I really can't tell them if they signed up for seeing the hot ads that we post here or for learning how to promote their products or services effectively but one thing that I can tell them is that what my site is all about.

I am going to change the text of the welcome email to include this information - about the forum - in my welcome email text.

In fact, this practice of describing your service in your welcome email should not only be for your forum but this also Newsletters, Shopping Carts and everything that allows people to register with you and you send a welcome email to them after they have signed up.