Is it called Spamming if you send emails to people in forums and message boards who are looking for something in particular and you provide them a source in email form? What are the rules to this? Thanks
You have to read the rules that are given by forum, one thing is sure that if you break forum rules you'll be banned !
If it's actually relevant to them in what they want and not linked in some obscure way, say they're looking for a domain but you offer a marketing service, then it would be ok. If you feel like it is actually spam then it probably won't be ok.
If you send me selfpromotion when I did not ask for it, this is spamming to me. If you build a relation and you tell me that you can do this and that, there's more chance you'll get my business
Why not have your signature linked to your website/product? Then people can click on it if they are interested.
Always PM first, but before that, I would join the discussions and ask them (or tell them what you can offer) to PM you if they're interested.