Email Deliverability Checklist for 2026
Authentication (the foundation)
Email authentication is non-negotiable in 2026. Google and Yahoo enforce SPF and DKIM for all senders and require DMARC policies for bulk senders. Start with your DNS records: publish an SPF record that includes all services authorized to send email for your domain. Set up DKIM signing through your email API provider — AISend generates DKIM keys automatically when you add a domain. Publish a DMARC record starting with p=none for monitoring, then tighten to p=quarantine once you've confirmed all legitimate senders are authenticated. Verify your setup with tools like MXToolbox or the AISend dashboard's domain verification feature. Authentication alone won't guarantee inbox placement, but without it, nothing else matters.
Sender reputation management
Your sender reputation is a score that ISPs assign to your sending domain and IP based on your sending history. It's influenced by bounce rates (keep under 2%), spam complaint rates (keep under 0.1%), engagement metrics (open rates, click rates), sending volume consistency, and the age of your sending domain. To build and maintain good reputation: warm up new domains gradually, never buy or scrape email lists, remove inactive addresses regularly, and monitor blacklists. Use a dedicated sending domain for transactional email (e.g., mail.yourapp.com) separate from your corporate email domain. This isolates your transactional reputation from any marketing email issues.
Content optimization
Email content affects deliverability more than most developers realize. Avoid spam trigger words in subject lines (free, urgent, act now, limited time). Maintain a reasonable text-to-image ratio — emails that are mostly images trigger spam filters. Include a plain text version alongside your HTML for accessibility and deliverability. Keep your HTML clean and lightweight — bloated HTML with excessive inline styles can trigger filters. Don't use URL shorteners (they're associated with spam) — use full, visible URLs. Include your physical address in the footer for CAN-SPAM compliance. AISend's content scoring analyzes all of these factors before sending and gives you a deliverability score with specific improvement suggestions.
List hygiene and bounce handling
Maintain a clean sending list by validating email addresses at signup (format check + MX record verification), implementing double opt-in for marketing emails, removing hard bounces immediately (never retry), treating repeatedly soft-bouncing addresses as invalid (3 consecutive soft bounces), and removing addresses that haven't engaged in 6+ months. Build a suppression list that includes all bounced addresses, unsubscribes, and spam complaints. Check every recipient against this list before sending. AISend maintains a provider-level suppression list automatically, but your application should maintain its own list for faster checking and domain-specific logic.
Monitoring and continuous improvement
Set up monitoring for key deliverability metrics: delivery rate (should be above 98%), bounce rate (below 2%), spam complaint rate (below 0.1%), and open rate (benchmark varies by email type — transactional emails should be 60%+). Monitor these metrics daily and set up alerts for deviations. Check major blacklists weekly (Spamhaus, Barracuda, SpamCop) to catch listing before it affects deliverability. Review your AISend dashboard regularly for AI-generated insights and recommendations. When you see deliverability issues, investigate immediately — problems compound quickly as ISPs notice declining engagement. The difference between a 98% and 95% delivery rate might seem small, but for a SaaS sending 10,000 emails per month, that's 300 users who didn't get their password reset or invoice.
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