The solution to the problem of getting the domain in black leaves spam

Good day, dear freelancers. A couple of months ago, our domain – hqhotels.ru was infected by malicious code that sent out the spam messages. The problem was solved, the defense delivered, but now, faced with the consequences – many messages are not delivered, the Berzerker comes with 550й error with different email services including mail.ru and to outlook. Who can help – write options and the cost of the work.