YouMail utilizes a carrier feature called Conditional Call Forwarding (CCF) to receive your missed calls and connect you to our voicemail system.
Metro by T-Mobile has the Call Forwarding feature available for $1 per month. You can add this feature by contacting Metro by T-Mobile Customer Service or you can add it directly from your MyMetro app.
Once this feature has been added, you can activate YouMail on your Metro by T-Mobile device by following this link > selecting the drop down arrow next to [Edit] > selecting "Forward to YouMail."