(|(mail={a})(uid={a})(mailaddress={a})(cn={a}))
2. Example: The Allowance Query String can be used for Mail Relay SMTP Authentication Profile
more Infos about the cisco ironport Mail ESA Box config:
https://www.cisco.com/c/en/us/td/docs/security/ces/user_guide/esa_user_guide_11-1/b_ESA_Admin_Guide_ces_11_1.html