A sorting system for flat items of mail has N1≧2 parallel-connected groups of storage modules for simultaneously storing a multiplicity of items of mail. The items of mail are fed through N2≧1 parallel mail feeders to in each case a plurality of groups, and discharged via N3≧2 parallel mail dischargers from in each case a plurality of groups. A process controller controls a joint storing of items of mail from a stream of mail into storage modules belonging to at least one group and simultaneously controls discharging of jointly deposited items of mail from storage modules belonging to at least one other group. It is thus possible to intersperse the streams of mail with little or no intersecting, accompanied by a high throughput rate through the sorting system.