Rabbi Yitzchak Zalman Poizner served as a community rabbi and was active in spreading Judaism, corresponding with the Rebbe in the 1950s and 1960s. No reliable published biography is available; the summary below is drawn from the letters themselves.
Several letters concern his rabbinate: the renewal of his contract and the role of a true community rabbi (IK 3590), taking initiative in difficult tasks and overcoming obstacles (IK 3936), the absolute necessity of practical mitzvah observance (IK 3269), expanding Jewish activities and spreading the wellsprings (IK 4498), and arranging names alphabetically to prevent complaints (IK 2027). Halachic letters discuss the placement of the paroches inside the aron kodesh and its sources in halachah (IK 3044, 3114). Others give guidance on publishing a Torah book and promoting it effectively (IK 6079), and on three aspects of milah, time-bound mitzvos, and true freedom (IK 8909).
See also: Leadership – The community rabbi; Halachah and custom – Asking a Rav and halachic questions.