Outlook and remote users

We use Outlook w/ Exchange server in my office and I have several users who leave the office to work in field sites for months at a time. What is the best way to forward their email to a hotmail account for example and delete it from the main email system? I tried the out of office assistant but it doesn't always delete and archive old messages which causes mailboxes to reach the size limits that are set up. The deleted items folder is set to permanately delete after 1 day but doesn't always work.

Any help would be great