ds-7608ni-e2/8p/a firmware

Gold morning to all... i have this NVR: DS-7608NI-E2/8P/A with firmware: V3.4.0_151103, i can't send any email alert, and sometimes he reboots by himself! before I had another NVR, the same but wihout /A with firmware V3.4.90_161080 I have 1 questions: 1) DS-7608NI-E2/8P/A or DS-7608NI-E2/8P...