Agents and brokers should keep all transaction and client emails indefinitely. This isn't a huge burden, but it is required that they be in a form that can be easily read at the current time. So you might want to convert them to something besides the Outlook format, perhaps Adobe Acrobat files.
File these emails in print format and on a CD or DVD for future retrieval. An example was given that you could possibly be accused of "virtual document shredding" if you delete emails or over-write them with future backup activities. So keep them all, because someone else may have their own copies.
