How do I synchronize with Outlook Express?

You can't! All versions of Inbox running on Handheld, Handheld PC Professionals, Palm-size and Pocket PCs do not synchronize with Outlook Express. Actually, the problem is not with Inbox so much as with ActiveSync since it doesn't work with anything other than Outlook or Schedule+.

Perhaps some third party company could write an ActiveSync pluggin for Outlook Express? Until then, it cannot be done.