If you use Blind transfer out of the vmail.

the call will return to voicemail if the station is forwarded to vmail or when the system recall timer is met, if the station is not forwarded to vmail.

keep in mind it looks at both, so if you have it forward to vmail after 6 rings and the recall timer is set to recall after 4 rings. It will follow the recall timer.

we usually set up a station to forward to voicemail after about 4 rings.