Multiple mailboxes permitted on a corporate MDM-managed iPad/iPhone: a mix of iOS email client & MobileIron Email+

A user is using corporate MDM-managed iPad & reading his corporate emails
from this device (that is in encrypted partition) using MobileIron's Email+, a
more secure form of email client compared to Apple's native email client.

Now this user requests for 2 common mailboxes to be configured on his iPad
so that he could read emails sent to his group.  Our MDM admin told us Email+
can't support the additional mailboxes (I'm not sure if this is true but I heard
the admin chap has logged a case with MobileIron).

What are the risks?  Can we create Exchange rules (as the emails had to
go to Exchange first before going to Email+ (or any other email clients) to
auto-forward one copy of emails sent to common mailbox to this user.

We had previously migrated users from Apple's email client to Email+ for
security reason, so don't want to go back to the old way of using Apple
email client