Container closure having a container side and a cover side and comprising a ring element which comprises a ring aperture and a first circumferential sealing surface, a lid element circumferentially connected with and extending inward from a circumferential sealing lip and towards said container side through said ring aperture, said lid element being formed of an elastomer material and being tapered to have an indented cover side and a bulged container side, wherein the maximum depth of the indentation relative to the outermost cover side part of the lid element is at least two centimeters, said circumferential sealing lip forming the outer edge of said lid element and comprising a second circumferential sealing surface matching said first circumferential sealing surface to form together therewith, in a sealing configuration, a circumferential sealing contact, a circumferential connection between said lid element and said ring element, said connection comprising a circumferential recess and a circumferential protrusion and being arranged on the container side of said lid element at a position between said sealing lip and the outermost container side part of the lid element, a ring chamber formed between said ring element and said lid element and sealed by said sealing contact in the sealing configuration, at least one channel formed in said lid element and extending from a respective container side channel inlet outside said ring chamber to a respective channel outlet in said ring chamber, wherein said lid element forms a liquid impermeable barrier between the container side and the cover side, and wherein a non-sealing configuration is temporarily achievable by reversibly deforming said sealing lip, characterized in that said container side channel inlet is located closer to the outermost container side part of the lid element than said connection and said channel outlet is located closer to the sealing lip than said connection. a ring element which comprises a ring aperture and a first circumferential sealing surface, a lid element circumferentially connected with and extending inward from a circumferential sealing lip and towards said container side through said ring aperture, said lid element being formed of an elastomer material and being tapered to have an indented cover side and a bulged container side, wherein the maximum depth of the indentation relative to the outermost cover side part of the lid element is at least two centimeters, said circumferential sealing lip forming the outer edge of said lid element and comprising a second circumferential sealing surface matching said first circumferential sealing surface to form together therewith, in a sealing configuration, a circumferential sealing contact, a circumferential connection between said lid element and said ring element, said connection comprising a circumferential recess and a circumferential protrusion and being arranged on the container side of said lid element at a position between said sealing lip and the outermost container side part of the lid element, a ring chamber formed between said ring element and said lid element and sealed by said sealing contact in the sealing configuration, at least one channel formed in said lid element and extending from a respective container side channel inlet outside said ring chamber to a respective channel outlet in said ring chamber, wherein said lid element forms a liquid impermeable barrier between the container side and the cover side, and wherein a non-sealing configuration is temporarily achievable by reversibly deforming said sealing lip, characterized in that said container side channel inlet is located closer to the outermost container side part of the lid element than said connection and said channel outlet is located closer to the sealing lip than said connection.