GFI MailEssentials
WorldSecure
PGP Extension
ARCryptoMail
CryptoEx for MS Exchange
Mark Wilson Classify
Signed, Sealed, Delivered
MailSecure Plug-in
Entrust/Express
ExSign
PGP for Personal Privacy
Ascom IDEA@exchange
RPK InvisiMail
TrustedMIME
Secure Exchange Servers
Krypto
Boldon James SAFEmail.mil
TFS Encryption
S/MIME Everywhere
VeriSign
Compaq Exchange (SE)
Encryption Plus
TFS Secure Messaging - Server
Mail Vault
Policy Patrol
Arcot WebFort
MailRecall
securiQ
eFilter
IronMail
iMira Screening
SuperScout
eMailTrackerPro