In this case, plaintiff sought to invoke the presumption of invalidity to show that the trial court lacked jurisdiction to rule on posttrial motions. Judgment in favor of defendant is affirmed, where: 1) the presumption set forth in Code of Civil Procedure section 1013a(3), for which service is presumed invalid if the postmark is more than one day after the date of deposit for mailing contained in the proof of service declaration, is a rebuttable presumption affecting the burden of producing evidence that must be affirmatively invoked by the party seeking to invalidate the service; and 2) plaintiff, the party seeking to invalidate the service here, did not affirmatively invoke the issue below.