Mail archiving mainly refers to online archiving, classified management, long-term retention and real-time query access of mail data, which is mainly aimed at the application of massive mail data and is an effective technology for data migration and management. Value: 1, tamper-proof, electronic proof guarantee 2, "separation of powers" easy audit 3, standardized management, legal compliance 4, prevention of data loss, preparedness 5, life cycle management, space recovery 6, rich service functions, improved work efficiency 7, mail data transposition, scientific "slimming" 8, unlimited online expansion of "green" investment 9.