The most important act in Ulmann's rabbinical career was the organization of the Central Conference of the Chief Rabbis of France, over whose deliberations he presided at Paris in May, 1856. In that year Ulmann addressed a "Pastoral Letter to the Faithful of the Jewish Religion," in which he set forth the result of the deliberations of the conference, which were as follows:
revision and abbreviation of the piyyutim;
the introduction of a regular system of preaching;
the introduction of the organ into synagogues;
the organization of religious instruction;
the institution of the rite of confirmation for the Jewish youth of both sexes;
a resolution for the transfer of the École Centrale Rabbinique from Metz to Paris.