When updating contacts/leads I'd like to be able to check against a list of 10 (and growing) emails. If the record being updated/created matches one of the emails on the list, I want to throw a validation error e.g. "Person is blacklisted".
My initial thought was to just have a large validation rule on the Contact and Lead objects that checks the whole list of emails in the rule criteria i.e.
However, the list of emails grows by about 1 a month, and I want to avoid having to iterate this formula every time I want to add an email to the list.
How can I check a Contact/Lead record updates against a list of emails in a more efficient way? Queues?
P.S. I've had the Individual object suggested to me, but its functionality is limited, also, I don't believe it's necessary as my email list size is about 10 right now.