Rule of thumb when when dealing with system administrator user accounts (those that UIDs range from 1-99) should never be touched (unless you know 100% what you are doing). These user accounts tend to be needed for important system functions.
UIDs 1 through 99 are traditionally reserved for special system users
(sometimes called pseudo-users), such as wheel, daemon, lp, operator,
news, mail, etc. These users are administrators who do not need total
root powers, but who perform some administrative tasks and thus need
more privileges than those given to ordinary users.
Sendmail for example, is one such application that uses the
mail user if the default options are left intact. The
DefaultUser option in Redhat 7 defines the userID as
8 and the groupID as
12. These values match with the
mail user in your