Abstract: An automatic, signalling flag device for rural-type mailboxes. A large metal or plastic signal flag is hinged to the side of the mailbox and is aligned and mounted for pivotal movement in a plane which is laterally transverse of the mailbox. The flag has a raised position, a lowered position to which it can fall by gravity and has a hole through it. A rod is mounted to the exterior of the mailbox for retaining the flag in the raised position and releasing it upon opening of the mailbox door, permitting the flag to fall to its lowered position. The rod is slideably mounted to a fastener which is pivotally mounted to the mailbox rearwardly of the signal flag, extends forwardly to a position where it is bent into a bayonet which is extendable into the hole in the flag, then extends forwardly to an L-shaped bend at the mailbox door and extends across the front, exterior face of the door into pivotable connection with a front fastener means mounted in the door.