;emailbody=
;emailsubject=

; Change the from, body and/or subject, variables:
;     VM_NAME, VM_DUR, VM_MSGNUM, VM_MAILBOX, VM_CALLERID, VM_CIDNUM,
;     VM_CIDNAME, VM_DATE

and

;serveremail = notification@some_domain.tld

An asterisk reload or restart is required:

sudo asterisk -r reload