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Exchange Server Compatibility Information Exchange Server Version Compatibility 5.5 Yes 2000 Yes 2003 Yes 2007 Yes

Migrating from POP3 to SMTP
Author: Simon Butler, Exchange MVP, MCSE

If you have been using Small Business Server with a POP3 Connector, or your clients have been collecting email directly from the ISPs server, there comes the point where you want to switch over to direct email delivery. The concern is how this change can be done with the minimum of disruption to the users, without loosing any email and causing embarrassing non-delivery reports.

As with many things with Exchange, with careful planning this kind of change can be done with zero downtime at the server and minutes with each user.

This procedure is for a new Exchange server replacing a POP3 service from an ISP. You can adapt it at certain points if you are replacing the POP3 Connector on a Small Business Server. It applies equally to both Exchange 2003 and Exchange 2007, and their variants of the POP3 connector.

1. Build the Exchange server, configure it correctly for your external domain and test. Any test email messages for external accounts will go out correctly - replies will go to the existing POP3 mailboxes. 
2. Once you are sure it is working, configure all the user accounts as required.
   
   At this point you can pause, as Exchange is not actually managing the email.
    
3. Visit each user and change their Outlook to point at the Exchange server. Make sure that you change the delivery location to Mailbox instead of personal folders, then import the email content that was in their PST files in to their Exchange mailbox.
4. Configure Outlook to look at the existing POP3 account. This will be a secondary account.
   Email will flow out through Exchange and back in via the POP3 accounts.
   
   You are a little under pressure to do that stage quickly as internal email may get sent to the Exchange accounts instead of the POP3 accounts. Once those two stages are complete you can pause again, as the users will continue to operate in the normal way.
   
   Now you are ready to switch over. Remember that DNS changes take 48 hours to propagate, so you need to run with both solutions for at least that time. A good recommendation would be to leave both solutions in place for a further 24 hours to ensure that everything is caught.
   
   If you are using Small Business Server and the POP3 Connector, this is where you can use this procedure.
    
5. Ask the company who manages your external domain to change your MX records to point to your Exchange server. Remember that MX records are made up of two parts. The A record which is a host pointing at an IP address, and the MX record itself pointing at the host. An MX record cannot be an IP address.
6. Once the change has been made, you will see email coming in through Exchange almost immediately. Email will still come in via the old solution until DNS has fully propagated. Ask some of the more heavy users to keep an eye on how much email comes in on Send/Receive for the POP3 account.
7. Once you are sure that everything has been collected from the old POP3 accounts, remove the POP3 account configuration from the client machines or POP3 Connector and get the accounts deleted at the ISP.

If you are on a dynamic IP address then you should review our article on using a dynamic IP address with Exchange here.