However, she cautioned, for K-12 Apps for Education customers, Google should explain the reason for the eventual migration from Postini.

Google needs to ensure those customers are "comfortable with the move and how they get there to avoid any unnecessary security risks," Wettemann said.

Google Apps customers don't need to have a Postini license to take advantage of its e-mail security features in Apps, which will be offered at no extra charge, the Google spokesman said.

All Google Apps editions are free except the Business version, which costs US$50 per user for an annual license, or $5 per user per month without an annual commitment.