Deutsche Bank assumed that the mailbox rule’s presumption of delivery applied to the acceleration notice it allegedly sent by certified mail to Chai and Jintana Roongseang at their North Shore Wilmette residence before filing a mortgage foreclosure case.But the Roongseangs denied receiving the required notification. And because Deutsche Bank failed to send the notice by first-class mail, they argued that Section 15 of the mortgage obligated the bank to provide proof of actual delivery.Section 20 of the mortgage said …