Pursuant to 735 ILCS 5/2-206 (a), due inquiry shall be made to find the defendant(s) prior to service of summons by publication. In mortgage foreclosure cases, all affidavits for service of summons by publication must be accompanied by a sworn affidavit by the individual(s) making such "due inquiry" setting forth with particularity the action taken to demonstrate an honest and well directed effort to ascertain the whereabouts of the defendant(s) by inquiry as full as circumstances permit prior to placing any service of summons by publication.
Ill. R. Cir. Ct. Cook Cnty. 7.3