sender when checking recipients. If used indiscriminately, it reduces the
usefulness of callout caching.
+.new
.vitem &*hold*&
This option applies to recipient callouts only. For example:
.code
if the use_sender option is used,
if neither the random nor the use_postmaster option is used,
and if no other callouts intervene.
+.wen
.endlist
If you use any of the parameters that set a non-empty sender for the MAIL