Abstract: A single copy of an incoming message addressed to multiple recipients is stored as a shared message on a server and the message's size is determined. A recipient count indicates how many of the recipients of the message have mailboxes on the server. A total amount of storage that would be needed to store copies of the message in each of the recipient's mailboxes is calculated from the size of the message and the recipient count. The calculated total amount of storage is compared to a predetermined limit. A selection is made between storing multiple copies and storing only the single copy of the incoming message on the mail server responsive to the comparing.

Abstract: A mail server detects if an incoming message is addressed to multiple recipients, in which case redundant data storage is reduced. A single shared copy of the message is stored, and a reference message, which refers to the shared message, is provided to the addressed recipients. A record of the number of existing reference messages is maintained, and decremented as each reference message is deleted by recipients. When no reference messages remain, the shared message is also deleted. A record of recipients authorized to access the shared message is also maintained, and updated as recipients delete their reference messages.