Yes, VOICEMAIL is a Scrabble word!

Letter values in Scrabble US: V 4, O 1, I 1, C 3, E 1, M 3, A 1, I 1, L 1.

Is it a valid word?

VOICEMAIL is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a computerized system for answering and routing telephone calls; telephone messages can be recorded and stored and relayed

Also: voice mail.