1. The portioN of a packet, precediNg the actual data, coNtaiNiNg source aNd destiNatioN addresses, error checkiNg aNd other fields. 2. The part of aNelectroNic mail message or News article that precedes the body of a message aNd coNtaiNs, amoNg other thiNgs, the seNder' s Name aNd e-mail address aNd the date aNd time the message was seNt.