Dear employer,
I am certified specialist in the security field and I will be more than happy to help you out with the project you are having. Of course it will be great if I can get more information on the amount of mailboxes (server) that needs to be checked and the systems/servers (if such) that needs to be checked.
Also you will receive a free advice on how to protect further and improve security further.
Best regards,
Ivaylo