Can I offer my services to organizations through feedback forms or by emails indicated in contacts?

Question

Law in IT

To what extent is it legal to offer legal services? to persons through feedback forms on customer sites or by emails indicated on the contact pages? Does it matter if paid services are offered or free?
Those. interested in answers to the following questions

• Is it prohibited by the law of the Russian Federation,
  
• if it is prohibited, then under what conditions does liability arise, which, in turn, should be taken by the site owner in order to bring to responsibility,
  
• in what ways to offer site owners their service (we are not talking about mass mailing, but about some fairly limited list).
  

Answer 1

Apparently it's called spam. And of course you can, no one forbids calling / writing.

Answer 2

There is no statutory regulation for such activities.