The consensus among experts, marketers, and documentation sources is that using HTTP links instead of HTTPS links doesn't directly affect email deliverability algorithms. However, HTTPS is considered a best practice because it contributes to overall sender reputation, enhances user trust and security, aligns with modern security standards, ensures broader browser compatibility, and can indirectly improve engagement metrics, all of which positively influence deliverability. Google's preference for HTTPS-secured websites and its use as a ranking signal is often cited as an indirect influencer of email engagement. While not a primary driver, HTTPS plays a vital role in creating a secure, trustworthy, and modern email environment.