diff --git a/man/mdeliver.1 b/man/mdeliver.1
index 6fc6bdb..3df357c 100644
--- a/man/mdeliver.1
+++ b/man/mdeliver.1
@@ -74,6 +74,8 @@ the flags of the new message file to be
 .Xr mbox 5
 .Pp
 .Lk http://www.digitalpreservation.gov/formats/fdd/fdd000385.shtml "MBOXRD Email Format"
+.Pp
+.Lk https://cr.yp.to/proto/maildir.html "Using maildir format"
 .Sh AUTHORS
 .An Christian Neukirchen Aq Mt chneukirchen@gmail.com
 .Sh LICENSE