If your server is unix then you could try the file command. I've found this very reliable.

From the man page :-

NAME
       file - determine file type

SYNOPSIS
       file  [  -bcnsvzL ] [ -f namefile ] [ -m magicfiles ] file
       ...

DESCRIPTION
       This manual page documents version 3.27 of the  file  com<AD>
       mand.   File tests each argument in an attempt to classify
       it.  There are three sets  of  tests,  performed  in  this
       order:  filesystem tests, magic number tests, and language
       tests.  The first test that succeeds causes the file  type
       to be printed.

Maybe File::MMagic is based on the same technology.