exim: move to "Mail" menu

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/Config.in

@@ -857,6 +857,7 @@ source "package/sound-theme-freedesktop/Config.in"
 endmenu
 
 menu "Mail"
+source "package/exim/Config.in"
 source "package/fetchmail/Config.in"
 source "package/heirloom-mailx/Config.in"
 source "package/libesmtp/Config.in"
@@ -897,7 +898,6 @@ source "package/dnsmasq/Config.in"
 source "package/dropbear/Config.in"
 source "package/ebtables/Config.in"
 source "package/ethtool/Config.in"
-source "package/exim/Config.in"
 source "package/foomatic-filters/Config.in"
 source "package/fping/Config.in"
 source "package/gesftpserver/Config.in"