Sendmail, 3rd Edition

Name

FEATURE(nocanonify)

Synopsis

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 (Section 18.7.6). The nocanonify feature 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 the nocanonify feature 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 the nocanonify feature disables only one possible use of $[ and $] in the configuration file. If the pre-V8.9 nouucp feature 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 the nocanonify feature was declared.

Also note that the Modifiers=C equate (See this section) for the DaemonPortOptions option does the same thing as this nocanonify feature, 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]

The assumption here is that this will go to the local hub ...