1&1 email settings product is known for its awesome service around the world. So, you can get immediate assistance from the technical experts without any charges. Or you can try to resolve the error on your own. Both ways, the error must not be the cause of tension as it can be resolved easily. 1&1 email settings sometimes caused due to invalid certificate issues. To resolve this you have to enable the POP account configured in 1&1 email settings.