Sophos
Sophos email encryption appliance, safeguard mailgateway enables intelligent and centralized email security and data protection.
http://www.sophos.com/en-us/products/encryption/safeguard-mailgateway.aspx
Greenviewdata
Greenviewdata
http://www.greenviewdata.com/email-encryption/pdf/Zix_EE_Brochure_web.pdf
Mcafee
Mcafee
http://www.mcafee.com/us/resources/solution-briefs/sb-email-encryption-gateway.pdf
Djigzo
Djigzo offers open source products that allow companies to automatically secure email and protect against unauthorized access of email both in transit and at rest.
http://www.djigzo.com
Emea
Emea
http://emea.trendmicro.com/emea/products/enterprise/email-encryption/gateway
Symantec
Symantec
http://www.symantec.com/business/universal-gateway-email
Trendmicro
Email encryption solution that fits your gateway -based encryption, client user-driven email encryption, and even a secure email hosted solution.
http://www.trendmicro.com/us/enterprise/network-web-messaging-security/email-encryption/index.html
Group IQ.Suite
Group technlogies ag - virus protection, security, and content filtering for lotus domino and exchange 2000 enterprise email systems
http://www.group-technologies.com/en/products/products/crypt.php