Watchguard Firebox X20E Reference Manual page 16

Mime content types list
application/vnd.fujixerox.docuworks
application/vnd.fut-misnet
application/vnd.hp-HPGL
application/vnd.hp-PCL
application/vnd.hp-PCLXL
application/vnd.hp-hps
application/vnd.ibm.MiniPay
application/vnd.ibm.modcap
application/vnd.intercon.formnet
application/vnd.intertrust.digibo+
application/vnd.intertrust.nncp
application/vnd.intu.qbo
application/vnd.is-xpr
application/vnd.japannet-directory-service
application/vnd.japannet-jpnstore-wakeup
application/vnd.japannet-payment-wakeup
application/vnd.japannet-registration
application/vnd.japannet-registration-wakeup
application/vnd.japannet-setstore-wakeup
application/vnd.japannet-verification
application/vnd.japannet-verification-wakeup
application/vnd.koan
application/vnd.lotus-1-2-3
application/vnd.lotus-approach
application/vnd.lotus-freelance
application/vnd.lotus-organizer
application/vnd.lotus-screencam
application/vnd.lotus-wordpro
application/vnd.meridian-slingshot
application/vnd.mif
application/vnd.minisoft-hp3000-save
application/vnd.mitsubishi.misty-guard.trustweb
application/vnd.ms-artgalry
application/vnd.ms-asf
application/vnd.ms-powerpoint
application/vnd.ms-project
application/vnd.ms-tnef
application/vnd.ms-works
application/vnd.music-niff
12