Default webmail choosing option RainLoop and Roundcube

Dear Developer team, already developed a very exciting offer as well as already we have Roundcube and Rainloop mailboxes and by default, it was set to Roundcube.

 But you know we can't set the default mailbox as RainLoop. Please give us this option. It will be very helpful for me. It will help us to time-consuming because  I love RainLoop.