Exchange 2010 Question

Hello! I have a question regarding exchange 2010.  I am the IT Operations Manager and a task to do with Exchange 2010 but dont have too much experience as an Exchange Admin. At our company we have a hybrid office 365 environment still using an OnPrem exchange server. For some reason the old IT team would create a User Object and share out the users email to other users and instead of just creating a shared mailbox. Don't know why they did it this way. So we have called Claims with a mailbox called Claims@contoso.com for example. This mailbox is being shared to 10 other users. Now they are in the process of creating the claims dept their own cue in service now and want to use the claims@contoso.com as a forwarding contact that will forward emails to claims@service-now.com so that anyone sending an email to the claims mailbox will now open up a ticket in service now instead and can be handled by that team. This is where it becomes complicated. They want me to remove claims@contoso.com from the user object. Give object another email for example test-claims@contoso.com and then create a forwarding contact that will forward all emails going to claims@contoso.com > claims@service-now.com thus creating the service now ticket. I hope I havent lost you. My question is do all i need to do is change the existing email address assigned to the claims user object to test-benefits@contoso.com by un-checking the "Automatically update email addresses based on email address policy" tick mark in the email address tab on the exchange mailbox, then manually editing the address and selecting the new address as the Set as reply email, then just create a contact and forward the benefits@contoso.com email address to the appropriate claims@service-now.com email address? Is it that simple? I tried to do this with two fake users and even though i removed the old email address (changed it completely to something else) it seemed as if he kept getting emails to both the new address and the old, even though only the new address was listed with no other aliases. I hope I'm explaining this right.. Please help.