Before deleting any electronic media, review the Records Disposition Handbook to be sure you are not violating Records Retention Policies.
Review the following EMAIL Policy: http://www.rdc.noaa.gov/~foia/asdhome/rec-email-rev.htm

By law Federal records are all documentary materials including:

• letters
• memorandums
• completed forms
• statistical and narrative reports
• graphics
• photographs
• audio and video recordings
• maps
• architectural, engineering, and other drawings regardless of physical forms
• photographic prints and negatives
• motion picture film
• tape recordings
• electronic records

Records are created or received during the conduct of agency business, and preserved or appropriate for preservation because they constitute evidence or contain information of value. (44 U.S.C. 3301).

• Each agency is responsible for determining if the materials it creates meet this definition of a record.
• Paper records may be originals or copies, such as file copies of outgoing correspondence or copies forwarded for action.
• Multiple copies of the same document may each be a record if each serves a separate administrative purpose and if they are kept in separate filing or recordkeeping systems.

When a record exists in multiple formats, such as in paper and electronic form, then generally both the paper and the electronic copies are considered distinct records.