Exchange Mailbox in Different forest

Dear All,

Looking for suggestion on trust requirement.

Forest A (Exchange Mailbox) Forest B (Account Forest) Forest C (Resource Forest)

There is a forest Trust between Forest B and Forest C > Result users from forest B can login on VDI desktops.

Now we are going to introduce Exchange 2103 in our Org, we will create different forest A for the same.

We will create Trust between Forest A and Forest B > so that Users can access the mailbox

Now the question is do i need to create a Trust between Forest A and Forest C > As users will acess the mailbox from VDI environment from different forest.

Thanks & Regards

Ashish Gaur