Hi Everyone,
 
I am working on a requirement to check the Lead/Contact email address, against the email address on a separate custom object named "Do not call Log'. For example, if the email address of fake123452@fakeemail.com exists in the email field, on the "Do not call Log" object a user should not be able to create a new Lead/Contact with that same email address. The user should get an error message stating that 'Email address already exists…" I was thinking of creating a flow to run a loop over the "Do not call log" object to check if that email already exists, however, I can't determine a way to get a message to the user upon trying to save the lead/Contact record.
 
Does anyone have any suggestions or thoughts? Should this be done via Apex?