Tutorials

Cutover migration from Exchange Server 2003 on a SBS 2003 Standard to Office 365

Cutover migration from Exchange Server 2003 on a SBS 2003 Standard to Office 365

We will perform a ‘cutover migration’ as for most Small or Medium sized business with less then 75 mailboxes (max in SBS 2003) this is the easiest way. It requires you to perform the migration during hours nobody uses the mail server so the best time is over the weekend. This does not mean you need to work the whole weekend, it is just to migrate data and make Office 365 the primary mail server for your email domain.

When the migration is done and DNS records point to your Office 365 account we need to change settings for the Outlook profile and that can cause some issues but those are fixed in Email migration from SBS 2011 with Exchange 2010 to Office 365 and autodiscover settings in Outlook

Before you can start this migration you need an Office 365 account. If you do not already have that go here Office 365 Business Premium | Office 365 and choose a subscription that fits your needs. Most businesses will choose either Office 365 Business Premium or Office 365 E3.

A cutover migration implies that during the migration is running any email sent to ‘already migrated mailboxes’ will end up at your on-premise mail server. There is a way to overcome this problem by closing traffic on port 25 for the time the migration batch is running. You may wonder what will happen with email send to your domain when you close port 25 on your SBS? Not much because sending mail servers must be configured to keep trying for at least 4-5 days after the initial failure and by that time we will have changed MX records for your domain to point to Office 365 and mail will flow again. Now if the sending party is not configured according to 5.3.1.1 Sending Strategy this could cause a problem but to be honest this should not be your problem. So, if you think a lot of important mail is sent to your domain during migration just block traffic on port 25.

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