You can change that setting to the last seven days, the last two weeks or the last month, or you can set it up so you can view mail sent and received at any time. In Outlook on Windows Phone 7, get to the settings screen, then select "Sync settings-->Download e-mail from" and make your choice about how you want mail synced.
Setting it up on other phones generally takes a little more work. In Android, for example, you have to go into My Accounts and set up a new Corporate Sync Account. For the Domain/username field, you have to append the address of your Office 365 account to the front of your username. For example, if your Office 365 account is mydomain.onmicrosoft.com, and your username is pgralla, you'd enter mydomain.onmicrosoft.com/pgralla in that field. For the Server field, you enter m.outlook.com. Once you do that, it works and syncs as you would expect.
Administrative e-mail tools
Even though Exchange 365 is hosted in the cloud, rather than on your company's server, you still get a full suite of administrative tools. You can easily add new Outlook users, either singly or in bulk (via .CSV files), determine whether users get administrative rights, and so on.
There are also tools for migrating in-boxes from a company's server-based version of Exchange to the Office 365 cloud-based version. These tools won't work for people who have been using Outlook in concert with POP3-based mail, though. There is a migration tool for IMAP accounts, although that requires a bit of extra work.
You'll also find a variety of more sophisticated tools as well -- for example, you can set group permissions for performing tasks such as allowing people to search across multiple mailboxes. In short, you get the kind of administrative tools you expect with Exchange, even though you don't host Exchange yourself.
Unfortunately, this is also one of many examples of the poor overall integration in the Office 365 beta. When you're on the pages for managing Exchange, there's no navigation to any other part of Office 365 -- essentially you're in a silo that appears to be a dead end. You have to navigate back to Outlook, and from there use site-wide navigation. This is a problem that appears time and again throughout the suite.
Office 365 also offers a hosted version of SharePoint, which allows you to build team sites where everyone in your organization can collaborate on documents and share a common document library.
Creating and designing a new team site is surprisingly easy. You choose a design, theme color and so on, and then add elements such as images, tables and document libraries. Adding documents to a team site is exceptionally easy: Click an Add Document button, choose the file you want to upload, and your work is done.