Patent ID: 7587455

Claim:
A method for migrating messages from a source mailbox on a source mail server to a destination mailbox on a destination server, the method comprising: copying a first source message from the source mailbox to the destination mailbox to create a first destination message, the first source message having a first source message ID and a first set of source message state indicator values, and the first destination message having a first destination message ID and a first set of destination message state indicator values; and creating a migration cache file, wherein creating the migration cache file comprises: storing the first source message ID as a first stored source message ID in the migration cache file; storing the first destination message ID as a first stored destination message ID in the migration cache file; associating the first stored source message ID with the first stored destination ID in a message ID map in the migration cache file; storing the first set of source message state indicator values in the migration cache file as a first set of stored source message state indicator values, wherein the first set of destination message state indicator values are not stored in the migration cache file; and associating the first set of stored source message state indicator values with the first stored source message ID in the migration cache file; enabling email clients access to the source mailbox during a precopy operation, thereby enabling a user to experience no email access downtime during actual copying of messages from the source mailbox to the destination mailbox.