Isocor, a supplier of Internet messaging, directory and metadirectory software solutions, is being acquired by Critical Path, an e-mail and Internet messaging solutions provider, in an all-stock deal worth an estimated $287 million. The deal will see stockholders of Isocor receiving 0.4707 Critical Path shares for each Isocor share. Isocor, the headquarters of which is in California, employs 90 people in Ireland.