A method and system provide user management of electronic message transmissions between servers and client devices, particularly transmissions of files attached to electronic messages. The method and system operate to transfer selected attached files to and from a client device. When accessing electronic messages with attached files stored at a server by a user, the attached files that satisfy a prescribed requirement are automatically downloaded from the server to the client device utilized by the user. The prescribed requirement may include maximum file size and download time, and approved list of file formats and senders. Preferably, the prescribed requirement is entered into the client device by the user. The prescribed requirement can vary depending upon the personal preference of the user. When forwarding received electronic messages with attached files, only the attached files that have been modified are uploaded from the client device to the server.