Advertisement Rules -
"If you plan to advertise a service or website, please note the following:
You are allowed a total of ONE thread regarding your service/site/whatever. If your website or service is mentioned by you in more then 1 thread it will be deleted everywhere and you will be banned from further postings."
Advertising a service can be a service provided by a spell caster whether contact is by website or email address. It's completely fine to do so. Yes, people will post advertisements in the wrong forum section, but this is why Editors, Moderators, and the Admin moves them to the Advertisement forum section where they belong. Note that in the decongestant paragraph of the rules quoted the "/whatever," this does not necessarily have to be your specific service despite seeming so. As long as the advertisement is within the advertisement rules and general site rules, it's perfectly fine. Otherwise, it is likely that the advertisement will be deleted - such as being spam posted.