What are the most common ESP-related deliverability issues?

• Many deliverability problems trace to ESP configuration or infrastructure issues rather than content or list quality.
• Authentication misconfiguration:
• SPF records missing ESP includes
• DKIM not properly set up or key mismatch
• DMARC alignment failing due to domain mismatches
• Custom domain setup incomplete
• Shared IP reputation:
• Other senders on shared pools causing problems
• ESP not adequately managing pool quality
• Being stuck in a low-quality pool despite good practices
• IP warmup failures:
• Sending too much too fast from new IPs
• Not following ESP warmup guidance
• Warmup interrupted or inconsistent
• Bounce handling issues:
• ESP not suppressing bounces properly
• Continuing to send to invalid addresses
• Misclassified bounces
• Tracking domain problems:
• Shared tracking domain blocklisted
• Custom tracking domain not configured
• SSL certificate issues on tracking domains
• Platform-specific issues:
• ESP limitations on sending speed
• Queue delays during high-volume periods
• Technical issues on ESP side affecting delivery

Check ESP documentation, verify your configuration, and use their support when troubleshooting. Many issues have straightforward fixes once identified.