Ex tenants mail

Tenancy Deposits

We recently had our tenants evicted by the bailiffs for non payment of rent. They have left a trail of debt with letters arriving daily looking very official. Some mail had been left by the tenants opened and discarded on the floor. All were demands for money and one was for a Distressed warrant! No forwarding address. I contacted the senders and explanied tenants had moved out.
New tenants moving in soon. What should I do regarding the un opened mail. Is it legal to open the letters adressed to ex tenants, as I don't want another disstressed warrant arriving when the new tenants move in. Any advice? Thanks.