The format of the file is that of the sendmail :include:-style list, where each line may be one or more comma-separated recipient addresses. For more on the .forward file format, see aliases(4).
Care must be taken to avoid creating addressing loops in the .forward file. When forwarding mail between machines, be sure that the destination machine does not return the mail to the sender through the operation of any NIS aliases. Otherwise, copies of the message may ``bounce''. Usually, the solution is to change the NIS alias to direct mail to the proper destination.
A backslash before a username inhibits further aliasing. For instance, to invoke the vacation program, user js creates a .forward file that contains the line:
\js, "|/usr/bin/vacation js"In this example, one copy of the message is sent to the user, and another is piped into the vacation program.
An alternative to the sendmail .forward file is maildelivery(4), which is used for similar tasks such as forwarding, appending messages to files, or piping messages to programs. One such program is the vacation(1) program, which can be used in conjunction with .maildelivery to create automatic replies to mail while a user is away on vacation. The Vacation Notification Manager, accessible via the CDE desktop, allows a user to configure the vacation notification. See Vacation Notification Manager in Vacation Notification Manager for details.