Archiving is not done automatically on the server side with our exchange email provider. The recommended course of action to maintain the size of your mailbox is to set up auto archiving locally in Outlook. AutoArchive will move email messages over 6 months old from your mailbox hosted on the Exchange server to an archived .PST file on your local computer. Please keep in mind, archived messages will not be viewable through Outlook Web Access because they are no longer stored on the Exchange server. However, they will be available in your Archive folder within Outlook locally.
To setup auto archive on your mailbox locally in Outlook, click the File tab and then the Options button. Next, click on the Advanced tab and click on the AutoArchive Settings button. Outlook automatically archives items every 14 days, sending items that are over six months old to the archive file listed in the AutoArchive dialog box. The default time settings should be fine for most users. Select how often you want it to run, prompt before the feature runs, where to move items, and other actions you want to happen during the process. Make sure the "Delete expired items (e-mail folders only)" checkbox is unchecked, and make sure that the "Permanently delete old items" radio button is not selected. After you’ve made your selections, click OK.
If you filter your mail into multiple folders, you may want to set different AutoArchive schedules for each mail folder. To do this, right click on the email folder, select Properties, and select the AutoArchive tab. Select "Archive this folder using these settings." After you have made the appropriate changes, click OK to save the changes.