The biggest mass emailer in the world, Epsilon, recently suffered a security breach as outlined in this press release: http://www.epsilon.com/News%20&%20Events/Press_Releases_2011/Epsilon_Notifies_Clients_of_Unauthorized_Entry_into_Email_System/p1057-l3 .
This carries some dangers of spam being sent to these stolen email addresses, spoofing the legitimate customers of Epsilon. There is an easy defence against this: DKIM. Symantec Messaging Gateway supports DKIM filtering and allows to defend against spoofing attacks based on Epsilon's security breach.
Thank you for the info.
checking SPF will of course also help, since Epsilon also uses SPF.