Recipe 4.1 Adding Domains to All Sender Addresses

Problem

You have been asked to configure sendmail to add a hostname to every header sender address, even when the input address has no hostname part and the mail is being delivered by the local mailer.

Solution

Add the always_add_domain feature to the sendmail configuration. The command that you add is:

 dnl Add the domain to all sender addresses FEATURE(`always_add_domain') 

Using Recipe 1.8 as a guide, build and install the sendmail configuration and then restart sendmail.

Discussion

The always_add_domain feature causes sendmail to make sure that every sender address includes a hostname part. By default, sendmail does not add a hostname part to the sender address when the address has no hostname part and the local mailer is delivering the mail. Thus, mail from the address alana goes through the local mailer's header sender process unchanged when the default configuration is used, as this test shows:

 #  sendmail -bt -Cgeneric-linux.cf  ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> >  /tryflags HS  >  /try local alana  Trying header sender address alana for mailer local canonify           input: alana Canonify2          input: alana Canonify2        returns: alana canonify         returns: alana 1                  input: alana 1                returns: alana HdrFromL           input: alana MasqHdr            input: alana MasqHdr          returns: alana HdrFromL         returns: alana final              input: alana final            returns: alana Rcode = 0, addr = alana >  /quit  

Rerunning the test after adding the always_add_domain feature to the configuration shows a different result:

 #  sendmail -bt  ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> >  /tryflags HS  >  /try local alana  Trying header sender address alana for mailer local canonify           input: alana Canonify2          input: alana Canonify2        returns: alana canonify         returns: alana 1                  input: alana 1                returns: alana HdrFromL           input: alana AddDomain          input: alana AddDomain        returns: alana < @ *LOCAL* > MasqHdr            input: alana < @ *LOCAL* > MasqHdr          returns: alana < @ chef . wrotethebook . com . > HdrFromL         returns: alana < @ chef . wrotethebook . com . > final              input: alana < @ chef . wrotethebook . com . > final            returns: alana @ chef . wrotethebook . com Rcode = 0, addr = [e-mail] >  /quit  

Here, the address goes in as alana and comes out with the hostname added as [e-mail].

See Also

Recipe 4.4 shows how the always_add_domain feature can be used with masquerading. The sendmail book covers always_add_domain in Section 4.8.4.