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4Site's Email Deliverability Playbook 
Deliverability isn’t magic, it’s management.
For nonprofit communicators, ensuring your emails reach their destination is paramount. This guide is a collection of the best practices I’ve collected from 20 years of coding email. It also includes some of the tools we use at 4Site to improve the reputation, reliability, and reach of our clients’ every send.
~ Bryan Casler, Vice President of Digital and AI Strategy
Here are some of the essential tools I’ll be referencing:
Use each section’s Audit checklist for strategies on optimizing your email program.
Knowing where your messages actually land (inbox, spam, or nowhere at all) is fundamental. Most email platforms report “delivered,” but that only means “not bounced.” Tools like Everest’s Inbox Placement Monitoring and Litmus’s Email Previews close this gap, showing true inbox placement across 140+ mailbox providers.
For nonprofits, this visibility matters most during critical moments (Giving Tuesday, end-of-year drives, or urgent advocacy campaigns) when even a small placement dip can mean thousands in lost donations.
Consider:
Common Pitfall: Relying solely on open rates to infer deliverability. If an entire segment’s open rate drops overnight, you may be landing in spam without realizing it. Everest and Litmus confirm the where, not just the what.
Audit:
☐ Inbox placement tested monthly across all major mailbox providers using a reliable tool.
☐ No significant spam or “missing” spikes in recent reports.
☐ Placement trends remain consistent across domains and campaigns.
☐ Benchmarked inbox rate meets internal target (≥95% for core lists).
Authentication is the foundation of deliverability. Everest continuously monitors SPF, DKIM, and DMARC to ensure each message is properly aligned. When these break, even temporarily, inbox providers lose trust fast.
Nonprofits often juggle multiple systems (CRMs, advocacy tools, newsletters) and each may send from a different subdomain. If one isn’t authenticated, it can damage your entire domain’s reputation. Everest’s automated checks surface misconfigurations and flag unauthorized senders.
Beyond basic authentication, your technical infrastructure can also affect placement:
Consider:
Nonprofit Example: An advocacy team discovered through Everest that their event vendor was sending confirmations from an unauthenticated subdomain. DKIM failures explained Gmail spam placement doubling overnight. Once the SPF record was updated, inbox rates recovered in two days
Audit:
☐ SPF and DKIM alignment at 100% across all sends.
☐ DMARC record published and reporting enabled.
☐ No unrecognized IPs or unauthorized senders in monitoring reports.
☐ TLS enabled and reverse DNS correctly configured.
How you send matters as much as what you send. Erratic sending can look suspicious to inbox providers. Establish a predictable rhythm of communication, whether weekly newsletters, monthly updates, or seasonal appeals.
If you’re launching a new domain or IP, warm it up gradually. Send to your most engaged subscribers first, then scale volume 20-30% every few days while watching deliverability reports from tools like Everest or Litmus.
Consider:
Common Pitfall: Sending one giant appeal after months of silence. A charity that did this saw a 40% drop in Gmail inbox rates. They rebuilt trust by reintroducing smaller sends first.
Audit:
☐ Send cadence documented and consistent.
☐ Volume increases are gradual and logged.
☐ No unplanned spikes in inbox trend reports.
☐ Regular sending calendar maintained for each audience segment.
Your list’s health defines your reputation. Everest’s BriteVerify validation or similar services remove invalid or risky addresses before you hit send, while bounce and spam trap monitoring identify problem areas over time.
Beyond list cleaning, engagement signals now heavily influence inbox placement. Gmail and Outlook track opens, clicks, deletes, and replies to decide whether to keep your messages in the inbox.
Consider:
Common Pitfall: Retaining inactive subscribers “just in case.” Unengaged contacts drag down open rates, hurt reputation, and increase the odds of hitting spam traps.
Audit:
☐ Hard bounce rate <2% across all sends.
☐ Validation runs on every new or imported list.
☐ Unsubscribes and complaints synced across all systems.
☐ Inactives suppressed or targeted in a re-engagement campaign.
☐ Replies tracked and used as engagement signals when possible.
Even perfect infrastructure can’t overcome poor content or user experience. Platforms like Email on Acid and Litmus offer Content Testing to help identify spam triggers, broken links, and rendering issues before launch. Furthermore, frameworks like MJML are specifically designed to simplify responsive email coding, helping ensure your designs look great everywhere.
Deliverability is shaped by how recipients interact with your emails. Clear, authentic messaging and a frictionless experience drive engagement and reduce spam complaints.
Consider:
Common Pitfall: Hiding unsubscribe links or using image-only emails. Both lead to “Report Spam” clicks that quickly degrade deliverability.
Audit:
☐ All emails pass spam and design tests using tools like Email on Acid or Litmus.
☐ Mobile and desktop versions proofed before sending.
☐ Subject lines A/B tested for clarity and relevance.
☐ Unsubscribe and preference links are functional and easy to find.
☐ No broken links or non-secure URLs.
Deliverability isn’t static, it’s a living system. Tools like Everest’s real-time alerts and dashboards transform monitoring into prevention. Configure alerts for authentication failures, blocklist hits, spam trap activity, or sudden inbox placement changes.
Regular reviews turn your chosen monitoring platform into your early warning radar. Weekly checks catch issues before they snowball into inbox-wide penalties.
Consider:
Audit:
☐ Deliverability alerts are active for all major risk categories.
☐ Dashboards reviewed weekly; anomalies addressed within 24 hours.
☐ Deliverability metrics tracked alongside opens and conversions.
☐ Any triggered alerts documented with resolution notes.
Even great programs stumble. When inbox placement tanks or your IP gets flagged, having a plan in place saves time and reputation.
Common Pitfall: “Sending through the problem.” Continuing full-volume sends during a deliverability crisis digs the hole deeper.
Audit:
☐ A written recovery plan exists with clear thresholds for pausing sends.
☐ Recovery sends tests on seed lists before resuming full volume.
☐ Reputation (inbox rates, complaints) returned to baseline before scale-up.
☐ Root causes documented to prevent recurrence.
Deliverability isn’t a one-time project, it’s an ongoing discipline. Platforms like Everest by Validity, Litmus, Email on Acid, and development frameworks like MJML provide invaluable visibility and support consistent best practices that maintain trust.
By embedding authentication, cadence, engagement hygiene, subscriber experience, and recovery planning into your workflow, you turn deliverability from a guessing game into a managed system. When your emails consistently reach the inbox, your message—and your mission—can do their best work.
We hope that means you’re interested in turning this playbook into results. Our Support Retainer is the easiest way to do that. You get flexible access to a senior, cross-functional team across strategy, design, engineering, data, and CRM, all focused on shipping work that grows revenue and strengthens your digital stack!