I was about to do a O365 cutover migration from on-premise Exchange 2003, when I read the following:

You cant migrate public folders directly from Exchange 2003. If youre running Exchange 2003 in your organization, you must move all public folder databases and replicas to Exchange 2007 SP3 RU15 or later. No public folder replicas can remain on Exchange 2003.

That is from the following TechNet article:

https:/ /technet.microsoft.com/en-US/library/jj200758(v=exchg.150).aspx

So, if I install Exchange 2007 to coexist with Exchange 2003 and move the public folders, will that scenario be supported by a O365 cutover migration? or should I completely move to Exchange 2007 and get rid of Exchange 2003 prior to the O365 migration?

OR should I migrate the 300+ public folders to O365 some other way, skipping the Exchange 2007 migration.

That's for you to decide.

If you want a hybrid configuration, which is the best client experience for a migration as you can do it at any pace you want, you'll need to deploy an Exchange 2010 server and move everything off of and remove the Exchange 2003 servers.

There are plenty of other migration tools besides the one that the above vendor shill recommended, all of them more well-known and industry-tested.

Beware of vendor shill posts above and below after I've marked this one as