Hosted Email Add the following records to your DNS settings.  
(Note that your DNS settings are not at Duocircle, they are with your DNS provider.)

example.com       MX     10  mx1.mailhostingservice.com   (10 is the priority and must be entered.)

mail.example.com    CNAME    mail1.mailhostingservice.com

webmail.example.com    CNAME   www.mailhostingservice.com  

Backup Email Add the following record to your DNS settings.

example.com    MX     20  mx1.mailhostingservice.com   (20 is the priority and must be a higher number than the primary service MX.)

Front-end Email service and Forwarding Email service add the following record to your DNS settings.

example.com   MX   5 mx1.mailhostingservice.com (5 is the priority and must be entered.)

The TTL on all these records should be around 1 hour unless you are making changes in the near future.

Note: you should replace "example" with your domain name