adding local_hostname option to smtp configuration

doc/hgrc.5.txt

@@ -309,6 +309,9 b' smtp::'
     Optional.  Password to authenticate to SMTP server with.
     If username is specified, password must also be specified.
     Default: none.
+  local_hostname;;
+    Optional.  It's the hostname that the sender can use to identify itself
+    to the MTA.
 
 paths::
   Assigns symbolic names to repositories.  The left side is the

mercurial/ui.py

@@ -298,7 +298,8 b' class ui(object):'
         def smtp():
             '''send mail using smtp.'''
 
-            s = smtplib.SMTP()
+            local_hostname = self.config('smtp', 'local_hostname')
+            s = smtplib.SMTP(local_hostname=local_hostname)
             mailhost = self.config('smtp', 'host')
             if not mailhost:
                 raise util.Abort(_('no [smtp]host in hgrc - cannot send mail'))