The impact of spam trigger words, PDF attachments, and links on email warm-up and deliverability is nuanced. While keyword filtering is largely outdated, modern spam filters prioritize sender reputation, engagement, and authentication. Focusing on building a clean email list, using double opt-in, sending relevant content, and warming up your domain gradually are crucial for establishing a positive sender reputation. Attaching PDFs can negatively impact deliverability, and links, especially to external sites, should be limited during the initial warm-up phase. Monitoring sender reputation, testing emails for spam triggers, and using personalized tracking links can further improve deliverability.