Both voicemail and voice mail came onto the scene during the 1980s when the first answering machines were widely sold and used by businesses. After the beep, I’ll tell you which spelling is right.

Beeeeeeep.

Voicemail is a recorded audio message left when no one answers a phone call, as in I didn’t want to talk to that jerk, so I just let the call go to voicemail.

Voice mail, as two words, means exactly the same thing and is a variant spelling.

For many years, voice mail was more common in writing than voicemail. Stylebooks often listed the two-word spelling as its preferred style.

That has changed during the 2010s. Stylebooks and dictionaries now generally favor the compound/one word version. Often words that start as two become one in the English language.

I recommend going with the trend and using voicemail. If that spelling really bothers you, though, you still can use voice mail. Whichever spelling you go with, just be consistent with it in your manuscript.