Depends where it's coming from......
Two likely places are letterbox and drain channel at bottom of door.
The letterbox problems usually occur with the push in type as water just runs in, I usually stick a couple of strips of 2" wide tape across them.
Bottom of door problem is usually blocked drain holes so water fills channel up and runs inside, get a short length of wire and unblock them.
Can't stand doing doors with cloth as its a poor result due to all the fancy bits and mouldings you just can't get a cloth into..... WFP the lot