It may not be in your local rules, so you’ll want to check on this, but ‘The Model Rules’ are clear that every written, recorded, or electronic communication from a lawyer soliciting professional employment shall include the words, ‘Advertising Material,’ on the outside envelope, as well as at the beginning and ending of any recorded or electronic communication.
In other words, when you convey an unsolicited message in print or electronically, (as opposed to in person or by telephone), you must always state, “advertising material,” at the beginning and end.