Times have changed, however. On a modern UNIX system, the administrator may wish to use one of several available MTAs.
It would be difficult to modify all MUA software typically available on a system, so most of the authors of alternative MTAs have written their front end message submission programs so that they use the same calling conventions as sendmail(1M) and may be put into place instead of sendmail(1M) in /usr/lib/sendmail.
sendmail(1M) also typically has aliases named mailq(1) and newaliases(1M) linked to it. The program knows to behave differently when its argv is “mailq” or “newaliases” and behaves appropriately. Typically, replacement MTAs provide similar functionality, either through a program that also switches behavior based on calling name, or through a set of programs that provide similar functionality.
Although having drop-in replacements for sendmail(1M) helps in installing alternative MTAs, it essentially makes the configuration of the system depend on hand installing new programs in /usr. This leads to configuration problems for many administrators, since they may wish to install a new MTA without altering the system provided /usr. (This may be, for example, to avoid having upgrade problems when a new version of the system is installed over the old.) They may also have a shared /usr among several machines, and may wish to avoid placing implicit configuration information in a read-only /usr.
/usr/lib/mailwrapper utility is
designed to replace /usr/lib/sendmail and to invoke
an appropriate MTA instead of
sendmail(1M) based on configuration
information placed in /etc/mailer.conf. This permits
the administrator to configure which MTA is to be invoked on the system at
Other configuration files may need to be altered when replacing sendmail(1M).
/usr/lib/mailwrapperutility exits 0 on success, and >0 if an error occurs.
/usr/lib/mailwrapperwill print a diagnostic if its configuration file is missing or malformed, or does not contain a mapping for the name under which it was invoked.
|August 7, 2006||OmniOS|