sendmail, 4th Edition

${mail_host}

---

Saved $@ value for MAIL FROM: triple

V8.10 and above

Upon receipt of the MAIL FROM: address, a delivery agent is selected by the RHS of a parse rule set 0 rule, which defines a triple that contains three pieces of information for that address:

 $#  delivery_agent $@ host  $:address  

The $@ portion of the triple contains the host to which to connect for delivery. For example:

 wash.dc.gov 

Once that host is determined for the $@ part of the triple, it is copied to this ${mail_host} macro.

${mail_host} is transient. If it is defined in the configuration file or in the command line, that definition can be ignored by sendmail . Note that a $& prefix is necessary when you reference this macro in rules (that is, use $&{mail_host} , not ${mail_host} ).