sendmail, 4th Edition

The E Configuration Command

When sendmail executes (runs) a delivery agent (The Child on page 757), it passes to that delivery agent an environment that includes only the items described earlier. Some delivery agents, however, might require additional environment variables to function properly. For those special cases, sendmail offers the E configuration command to set individual environment variables that will be passed to all delivery agents:

Evar=value

The var is the environment variable that will be either defined or redefined. It is immediately followed (with no intervening space) by an equal-sign and then (again with no intervening space) by the value that will be assigned to it.

If the =value is missing, sendmail looks up the variable var in its environment and, if it is found, uses that value. If the = is present but the value is absent, the var is assigned an empty string (a single zero byte). If the var is missing, a variable name that is an empty string is used.

The var is looked up to see whether it is already a part of the delivery agent’s environment. If it is, it is redefined to be the new value. If it is not, it is added to that list of variables. If that addition will cause the list to exceed MAXUSERENVIRON variables (currently defined as 100 in conf.h, MAX... on page 120), the definition is silently ignored.

Whether or not the var was added to, or updated in, the delivery agent’s environment, it is always added or updated to sendmail’s environment with putenv(2). If ...