Tonnes of catalogues, brochures and other advertising mail across the Rhine and Ruhr areas of central and northeastern Germany will go undelivered.
About a million letters were also expected to go undelivered in Hamburg, Schleswig-Holstein and Mecklenburg-Western Pomerania.
Workers’ meetings are planned in many areas on Wednesday. Barring an agreement with Deutsche Post, Verdi has said it will call workers to vote on Friday on an unlimited strike that would start May 2.
Verdi and Deutsche Post were unable to agree over the weekend on wages, shifts and layoff protection for 130,000 workers across Germany. The strike began on Sunday night.