Carmela filed a complaint for specific performance against Diego before the Regional Trial Court (RTC) of Pasig City. Summons was sent to Diego at his stated address in Makati City through registered mail. However, Diego claimed he never received the summons because he had already moved to Quezon City six months earlier and did not inform anyone of his new address. Without being served with summons, Diego learned about the case from a common friend. Diego filed a special appearance through counsel, submitting a "Motion to Dismiss for Lack of Jurisdiction Over the Person" on the ground that he was never validly served with summons. Carmela opposed the motion, arguing that by filing the motion to dismiss, Diego voluntarily appeared and submitted himself to the jurisdiction of the court. Diego countered that his appearance was special and for the sole purpose of questioning jurisdiction, which does not constitute voluntary submission. Did Diego voluntarily submit to the court's jurisdiction? Explain your answer. (Bar 2026 Syllabus)