When focussing on the SMB (Small-Medium Business) market I find that alot of companies don’t yet have their own Exchange servers and are still using POP mail. With the age of virtual servers upon us it is easier then ever to sell them on Exchange when you are already selling them a physical server and Windows enterprise license.
Best practice I have found when doing the migration is to use a POP connector on your Exchange server. This allows for a gradual migration and eliminates any lost email during the time when you are changing over the MX records.
Microsoft includes a free POP connector with Windows Server 2003 SBS and yet for some unknown reason doesn’t include one with the real version of Exchange. Still, using SBS is in fact it’s own punishment so it’s not a huge loss.
I recommend the Exchange Connector product by Quantum Software Solutions. It’s really straight forward to use and very customizable. You get a 30 day free trial, which is all you need if you are only using it for migration purposes, though I think it is well worth paying for if you think you are going to use it on a ongoing basis.
Here is the link