If non-@code{nil}, generate all required headers before starting to
compose the message.
-The variables @code{message-required-mail-headers} and
-@code{message-required-news-headers} specify which headers are required.
+@vindex message-required-headers
+The variables @code{message-required-headers},
+@code{message-required-mail-headers} and
+@code{message-required-news-headers} specify which headers are
+required.
Note that some headers will be removed and re-generated before posting,
because of the variable @code{message-deletable-headers} (see below).