FAILSAFE RELIABILITY

In addition to its unrivaled speed, InterMail allows ISPs to guarantee subscribers their mail will never be lost. The key to this fail-safe insurance is InterMail's unique message-level journaling system, in which each message is stored as a pending transaction in a protected journal file. Even in the event of a total system failure, undelivered messages can be retrieved from the journal file up to the point of failure.
In addition, InterMail's reliability features include:

• Tolerance to Internet outages - temporary unavailability of different domains in the distributed Internet hierarchy poses no problem for InterMail; messages are stored on disk until the destination address once again becomes accessible.
• Support for hardware-based recovery strategies - disk mirroring, remote-site journaling, redundant servers and other reliability safeguards are accommodated in InterMail's flexible architecture.

AVAILABILITY

A successful commercial ISP mail service must be continuously available to its customers 24 hours a day, 7 days a week, without exception. Unlike messaging products adapted from corporate intranets and enterprise-oriented ISP environments, where downtimes are routinely tolerated occurrences, InterMail was designed to provide uninterrupted service availability, even during maintenance and upgrade operations. InterMail meets this objective through key design features that include:

Online backup, maintenance, and upgrades - routine operational tasks are performed in the background while the system is still running.

Online recovery - failure recovery, including message journal retrieval, can proceed while the system is running.

Server redundancy - supports use of multiple servers to assume operational load if a component fails.

Failover - supports use of designated "hot spare" servers with automatic switch-over scripts for rapid (under one minute) resumption of operational continuity if a primary server fails.

No single point of failure - any component can be safely brought offline and the system keeps running.