Migrating from Exchange to a Linux mail server

• Organizations moving from Exchange will likely have a large store of user e-mail, calendar, public folder, directory and other data to migrate. The longer the e-mail system has been in use, the greater the number of users, and the more complex the Exchange configuration, the longer it will take to complete the migration process. Industry averages for migration range from a few days or weeks for a simple migration to several months for a complex migration. What is interesting to note is that it can also take quite awhile just to upgrade from one version of an e-mail system to another.
• Not all Linux e-mail servers are equal. It is important to understand some key issues, such as whether the e-mail server can co-exist with Exchange for an extended period of time (so that a flash cutover is not required). Also, to what degree can messages and other data be faithfully retained (so, e.g., when e-mail is migrated, a user can continue to reply to e-mail such that the prior sender's e-mail address does not need to be retyped).

The advantages of Linux e-mail include: reliability, security, performance, cost-efficiency and freedom from licensing and technology lock-in. It will be important to select an e-mail system that supports the level of functionality your end users rely on in your current Exchange environment. Other considerations:

• High fidelity co-existence with Exchange and your existing directory, eliminating the need for a flash-cut migration to the next system. Specifically, this means retaining fidelity of messages, calendar interoperability, public folder sharing between Exchange and the next system.
• Minimize user impact in the migration process. This means transparent migration of the user's mailbox and little or no downtime for end users.
• Flexibility in your migration process. No two companies are alike, so you should make sure your supplier can support a migration accommodates your needs and timetable.