sendmail: use FQDN in default envelope sender

RFC 5321 requires the return path to be supplied with a proper domain
name.

Signed-off-by: Kaarle Ritvanen <kaarle.ritvanen@datakunkku.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/mailutils/sendmail.c b/mailutils/sendmail.c
index 824109d99..9455b4e7a 100644
--- a/mailutils/sendmail.c
+++ b/mailutils/sendmail.c
@@ -326,7 +326,6 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv)
         // we should start with modern EHLO
         if (250 != smtp_checkp("EHLO %s", host, -1))
                 smtp_checkp("HELO %s", host, 250);
-        free(host);
 
         // perform authentication
         if (opts & OPT_a) {
@@ -353,8 +352,11 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv)
 
         // got no sender address? use auth name, then UID username as a last resort
         if (!opt_from) {
-                opt_from = G.user ? G.user : xuid2uname(getuid());
+                opt_from = xasprintf("%s@%s",
+                                     G.user ? G.user : xuid2uname(getuid()),
+                                     xgethostbyname(host)->h_name);
         }
+        free(host);
 
         smtp_checkp("MAIL FROM:<%s>", opt_from, 250);