When a deed purports to convey a greater interest than the grantor was at the time possessed of, any after-acquired interest of such grantor to the extent of that which the deed purports to convey shall accrue to the benefit of the grantee; Provided, however, such after-acquired interest shall not inure to the benefit of the original grantee or his heirs or assigns, if the deed conveying said real estate was either a quitclaim or special warranty, and the original grantor in any case shall not be estopped from acquiring said premises at judicial or tax sale, upon execution against the grantee or his assigns, or for taxes becoming due after date of his conveyance.