A solenoid, in particular for media-controlling valves, includes in an armature space an armature movably acting on a tappet, and a coil carrying windings of a conductor. The magnetic core delimiting the armature space has a tappet boring that incorporates the axially moving tappet, and a boundary element, that consists of at least partly elastic material and is media- and liquid-proof, is provided between the tappet and the magnetic core. The boundary element includes a fastening area for a sealing connection of the boundary element with the tappet, a connection area for a sealing connection of the boundary element with the magnetic core, and an intermediate part provided between the fastening area and the connection area. The intermediate part surrounds at least part of the length of the tappet like a hose or sleeve.