Abstract: A mailbox signal having two adhesively mounted brackets, one a ferrule support lineally and rotationally journalling a flag on a flag supporting element, and the other bracket providing a door mounted rest releasing the flag on the flange supporting element by disengaging an extension of the flag supporting element upon opening the mailbox door. The construction utilizes a durable weather resistant material installable without the requirement of tools or mailbox modification. The signal is easily and neatly packageable for sale and usage.