Java pro with Linux and DNS experience to refactor and extend app

We have a business app that enables our selected clients to validate that their customers' email addresses remain valid by connecting to the appropriate email servers and checking if the username is still valid (SMTP check). It does several DNS lookups prior to the SMTP check to collect all the mx servers for each domain. It handles SMTP errors efficiently as well. The app was built in java and functions ok right now, but there are features that we need to add and the original developer is completely absorbed in another project so we have to bring in someone new to manage and extend this app. I am looking to develop a good relationship with an experienced java developer. We can break this project into several milestones: 1) Review the existing application and supporting apps like the database and it's API and document (comments in the codebase are ok) each function. 2) Recommend and implement efficiencies and a few relatively minor features. This milestone can be negotiated based on the exact features requested. 3) Build a web based front end with a basic admin panel that does what the command line interface does: Load lists of emails, process emails, output results. Just to be clear - we deplore spam and this has nothing to do with it.