voice mail vs voicemail

voice mail and voicemail both are nouns.

Word	Noun	Adjective	Verb	Adverb
voice mail	Yes	No	No	No
voicemail	Yes	No	No	No

As nouns, voice mail and voicemail are synonyms defined as:

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

voice mail (noun)	voicemail (noun)
a computerized system for answering and routing telephone calls; telephone messages can be recorded and stored and relayed	a computerized system for answering and routing telephone calls; telephone messages can be recorded and stored and relayed