Development and maintenance of a platform

We are running a platform and need a top JAVA programmer to handle the back-end development and maintenance of the platform in the long term. You will also need to be familiar with server management (AWS tomcat), and have a sound understanding of data security.
Initially, the first task is to insure that our system complies with AWS protocol when sending emails.
We have been targeted by robots and need to implement features to avoid this happening in the future. This will require the implementation of a captcha in the user registration process, and the creation and coding of a process to disable the automatic sending of email when an email address is invalid (bounce).
This is a large platform with multiple users and users type with require several automated emails to be sent to the registered users.
Here is the link to our development (uat website) https://uat.themarketpeople.com/TMP/Home? to give you an idea of what we are doing. The budget is just an initial estimation. Due to the size of the project, we expect that you will need to "have a look" before providing an accurate quote.
You will also need to be able to commit to a long time project.
The satisfactory delivery of this first task including the quality of programming and the compliance with the agreed timetable will give you the opportunity to lead the back_end development of the platform which will require your full commitment to the project.