This should not be to difficult. Setup your Exchange server. Your exchange mailboxes can have multiple smtp addresses associated with them. Setup two for each mailbox, user@xxxxxxxxxxx and user@xxxxxxxxxxxxxxxxxxxxxxxxxxx Also create a contact for every person that points to the Sendmail server. On the mailbox, have all the mail be delivered to the contact (called an alternate recipient in Exchange). Users will be able to access the mailbox with Outlook and send mail. They will not receive any mail on the exchange serer. It will all be delivered to the Sendmail machine. When you are ready to migrate users, forward the mail from Sendmail to user@xxxxxxxxxxxxxxxxxxxxxxxxxx and remove the alternate recipient. Once all the users are migrated, change your MX record to the Exchange server. This should allow you to perform the migration with 0 downtime. Dennis -----Original Message----- From: Aleksandar Brankovic [mailto:baleksandar@xxxxxxxxxxxxxxxx] Sent: Thursday, December 18, 2003 3:59 AM To: [ExchangeList] Subject: [exchangelist] sendmail to Exchange 2003 migration http://www.MSExchange.org/ HI all, So, i have a little interesting feature wich will ocupy me in next days. I have to migrate sendmail server with 1800 mailboxes, with averige 3000 mail flow a day to Exchange 2003 server. Major point is that the downtime must be 0 seconds. I saw some advices on net but I`m not shure that it works. Anyone with expirience, or some advice. Beer on me!(if eweryyhing works) Cheers ------------------------------------------------------ List Archives: http://www.webelists.com/cgi/lyris.pl?enter=exchangelist Exchange Newsletters: http://www.msexchange.org/pages/newsletter.asp Exchange FAQ: http://www.msexchange.org/pages/larticle.asp?type=FAQ ------------------------------------------------------ Other Internet Software Marketing Sites: Leading Network Software Directory: http://www.serverfiles.com No.1 ISA Server Resource Site: http://www.isaserver.org Windows Security Resource Site: http://www.windowsecurity.com/ Network Security Library: http://www.secinf.net/ Windows 2000/NT Fax Solutions: http://www.ntfaxfaq.com ------------------------------------------------------