Watchguard Firebox X20E Reference Manual page 14

Mime content types list
application/applefile
application/astound
application/atomicmail
application/cals-1840
application/commonground
application/cybercash
application/dca-rft
application/dec-dx
application/eshop
application/hyperstudio
application/iges
application/mac-binhex40
application/macwriteii
application/marc
application/mathematica
application/ms-excel
application/msword
application/news-message-id
application/news-transmission
application/octet-stream
application/oda
application/pdf
application/pgp-encrypted
application/pgp-keys
application/pgp-signature
application/pkcs10
application/pkcs7-mime
application/pkcs7-signature
application/postscript
application/prs.alvestrand.titrax+
application/prs.cww
application/prs.nprend
application/remote-printing
application/riscos
application/rtf
application/set-payment
application/set-payment-initiation
application/set-registration
application/set-registration-initiation
10
Generic Macintosh files
Astound Web Player
Atomic Mail
CALS (RFC 1895)
Excel spreadsheet
Word document
PGP encrypted (RFC 2015)
PGP keys (RFC 2015)
PGP signature (RFC 2015)
PostScript
Microsoft Rich Text Format
SET payment