The Alias to... field contains one or more of the following, comma-separated:

• address: Mail is forwarded to address, which is compatible with the RFC 822 standard.
• /file/name: Mail is appended to /file/name. See local(8) for details of delivery to file. Delivery is not limited to regular files. For example, to dispose of unwanted mail, deflect it to /dev/null.
• |command: Mail is piped into command. Commands that contain special characters, such as whitespace, should be enclosed between double quotes. See local(8) for details of delivery to command. When the command fails, a limited amount of command output is mailed back to the sender.
• :include:/file/name: Mail is sent to the destinations listed in the named file. Lines in :include: files have the same syntax as the right-hand side of alias entries.