Mac OS X Server v10.5: SMTP Relay is enabled for local subnet by default

Products Affected

Mac OS X Server 10.5

Symptoms

When you set up the Mail service on a new installation of Mac OS X Server v10.5, SMTP is restricted by default to the local subnet. Machines on this subnet can relay through your mail service without authenticating. In some cases, such as a home office server connected to the Internet via cable modem or DSL, the "local subnet" may include other cable or DSL subscribers outside the home office.

Resolution

If there are computers on your server's local subnet that you do not control, you should further restrict SMTP relay or require SMTP authentication. For instructions, see "Restricting SMTP Relay" and "Requiring SMTP Authentication" in the Mac OS X Server 10.5 Mail Service Administration Guide, available from Apple Support Manuals.

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