(a) In addition to the methods of service provided for in the Rules of Civil Procedure, service may be made by delivering a copy of the process to the department, but it is not effective unless
- (1) the plaintiff, which may be the department in a proceeding instituted by it, immediately sends a copy of the process and of the pleading by certified mail to the defendant or respondent at the last known address of the defendant or respondent; and
- (2) the plaintiff's affidavit of compliance with this section is filed in the case on or before the return day of the process, if any, or within such further time as the court allows.