`mail-envelope-from' doc clarification

* lisp/mail/sendmail.el (mail-envelope-from): Note that the buffer
should be narrowed before calling (bug#47616).

diff --git a/lisp/mail/sendmail.el b/lisp/mail/sendmail.el
index 9a4c8f3c665acca0aaae3e7047f2289e09ec9166..a64f0869981c866cdee2ccf4c15e82952447a6dd 100644 (file)
--- a/lisp/mail/sendmail.el
+++ b/lisp/mail/sendmail.el
@@ -962,7 +962,10 @@ the user from the mailer."
 
 (defun mail-envelope-from ()
   "Return the envelope mail address to use when sending mail.
-This function uses `mail-envelope-from'."
+This function uses the `mail-envelope-from' variable.
+
+The buffer should be narrowed to the headers of the mail message
+before this function is called."
   (if (eq mail-envelope-from 'header)
       (nth 1 (mail-extract-address-components
              (mail-fetch-field "From")))