Maximum time and storage
Q: Did you know that there is a maximum time for storing messages?
A: Periodically, the system does an automatic message purge. A mailbox's new or saved messages are purged after 30 days. A mailbox's undelivered messages are purged after 30 days also. An undelivered message is one that has been placed into the mailbox since the last time the mailbox holder logged into the mailbox. A new message is one that was in the mailbox during a prior session when the user was logged in, but the user has not specifically saved or discarded the message.
If you need to save a particular message beyond the 30 day maximum, you must send a copy of the message to yourself. Simply saving a message will not extend the 30 day storage; you must resend the message so that it will be considered a new message.
Also note that a maximum of 20 messages can be in your mailbox at any one time.