Even with SPF and DKIM authentication, low-volume emails often end up in spam due to factors affecting sender reputation and trust. These include low engagement, inconsistent sending patterns, problematic email content, poor list hygiene, and IP-related issues. Mailbox providers consider various signals, including sender reputation, user feedback, content characteristics, and the proper implementation of authentication protocols like DMARC. A new ESP or subdomain, strict DMARC policies, and missing reverse DNS records can also contribute to deliverability problems. Seed listing and IP warm-up are critical for establishing a positive sending reputation, especially for low-volume senders.