Is anthrax always fatal?

No. It can be treated with penicillin and other antibiotics. The pulmonary form of anthrax is the form most likely to be fatal.
No. Mortality rate for untreated cutaneous anthrax is 10 -20 percent but less than 1% with correct antibiotic tx. The mortality rate for inhalation anthrax is around 75% (50 - 90 %) even with antibiotic therapy. Mortality rate for gastrointestinal anthrax is about 50 % (25 -60%). Effect of early antibiotic tx is uncertain for gi. Meningitis due to anthrax is just about 100% fatal.