sendmail, 4th Edition

FEATURE(nocanonify)

Don’t canonify with $[ and $] V8.1 and later

Ordinarily, sendmail tries to canonify (add a domain to) any hostname that lacks a domain part, and to canonify (ensure a correctly formed domain) for any host with a domain. It does this by passing the unadorned hostname to the $[ and $] operators (Canonicalize Hostname: $[ and $] on page 668). FEATURE(nocanonify) prevents sendmail from passing addresses to $[ and $] for canonicalization. This is generally suitable for use by sites that act only as mail gateways or that have MUAs that do full canonicalization themselves.

The form for FEATURE(nocanonify) is:

FEATURE(`nocanonify')

If you only want hostnames without a domain part canonicalized, you can add a second argument like this:

FEATURE(`nocanonify', `canonify_hosts')

Note that FEATURE(nocanonify) disables only one possible use of $[ and $] in the configuration file. If the pre-V8.9 FEATURE(nouucp) is omitted (thereby including UUCP support), addresses that end in a .UUCP suffix still have the preceding part of the address canonified with $[ and $] even if FEATURE(nocanonify) was declared.

Also note that the Modifiers=C equate (DaemonPortOptions=Modify= on page 996) for the DaemonPortOptions option does the same thing as this FEATURE(nocanonify), but does so on a port-by-port basis.

Sending out any unqualified addresses can pose a risk. To illustrate, consider a header where the local host is here.us.edu:

To: [e-mail] Cc: jane@here, [e-mail] From: [e-mail] ...