The move is part of a corporate-wide data loss prevention initiative to avoid accidental loss of private or proprietary information, said Karl Anderson, network security manager for the pizza maker.
"We realised that e-mails being sent to partners and suppliers, such as insurance providers, may contain information like social security numbers that must be encrypted before sending," he said.
Domino's will encrypt e-mail between corporate headquarters in Ann Arbor and its 17 distribution centres across the US, and between key partners and suppliers.
Secure-mail will automatically flag e-mails with sensitive data and encrypt them automatically prior to sending. Recipients will be able to read protected messages without having to download and instal client software.
Anderson said decisions about encryption will be made based on pre-set policy, not by individuals on a one-off basis.