New sender email addresses often experience lower rates due to a lack of established reputation and trust with inbox providers. Filters are more skeptical and actively test new senders, assessing their address, content, IP, domain, and DKIM signing domain. Factors such as low engagement, high bounce rates, inconsistent sending volumes, and shared IPs can negatively impact deliverability. Warming up IP addresses, authenticating emails, focusing on engaged users, maintaining clean lists, and monitoring sender reputation are crucial for new senders to build trust and improve deliverability rates.