Cant add Own Mail server, "This email address is already in use for a customer. Please use another e

Isaac_VCT

Trying to add our support email address as “own mail server”. (Office 365)

In the past emails had been sent to the queue from this address which created a "customer" with this email address.

Now when adding this address as "Own mail server" we get the error “This email address is already in use for a customer. Please use another email address.”

So we deleted this address from customers list in administration.

We also deleted any tickets that had been linked to this customer. 

However we still get the error. The customer must be hidden in a database somewhere(?) causing the app to think it still exists.

Any help appreciated.

Thanks,

Isaac