Get more campaigns into the inbox—not the spam folder—with a practical, end-to-end plan that improves authentication, sender reputation, list quality, and engagement.

Overview

Deliverability is no longer a “set it and forget it” checkbox. Inbox placement hovers in the low-to-mid 80% range globally—meaning roughly 1 in 6 legitimate marketing emails may never reach the inbox under typical conditions [1]. Some reports estimate that in 2025 only 60% of emails reached the visible inbox, with 36% routed to spam [4]. For CMOs and digital marketing leaders, that gap translates directly into lost pipeline, skewed attribution, and rising customer acquisition costs.

Mailbox providers increasingly weight authentication + reputation + engagement as a system. Validity’s benchmark reporting highlights rising spam placement and the ongoing distortion of opens due to privacy changes, pushing teams to optimize around deeper engagement signals—clicks, replies, saves, and positive user actions [1]. Meanwhile, large providers have tightened sender requirements around SPF, DKIM, and DMARC alignment, turning technical hygiene into a growth prerequisite [1].

The best deliverability programs aren’t siloed. When you integrate SEO intelligence, content performance, and social listening into email strategy, you send more relevant campaigns (higher engagement), use language your audience already responds to, and reduce “this is spam” behavior. The 10 strategies below are designed as a step-by-step blueprint you can implement this quarter.

1) Authenticate correctly (SPF + DKIM) and confirm alignment

Authentication is table stakes. SPF validates whether a sending IP is authorized for your domain (RFC 7208) [27], and DKIM cryptographically signs messages so mailbox providers can verify integrity and domain identity [5]. Passing checks isn’t enough—misalignment (e.g., DKIM signing domain doesn’t match the visible “From”) can still trigger filtering in modern enforcement regimes [1].

Implementation steps

• Publish one SPF record per domain. Include only the vendors that truly send mail.
• Enable DKIM signing in every ESP, CRM, and transactional mail system you use.
• Validate alignment: ensure your From domain, DKIM d= domain, and SPF domain strategy are consistent with your DMARC alignment plan (see Strategy #2).

Example

A B2B SaaS adds a new event platform that sends from events.vendor.com while the visible From is brand.com. SPF passes for the vendor subdomain, DKIM signs a vendor domain, and messages begin drifting into Promotions or Spam. Fix: route sends through a branded subdomain (events.brand.com) and ensure DKIM signs brand.com or an aligned subdomain—restoring consistent provider trust signals.

Actionable takeaways

• Audit every sender that touches your domain, including “one-off” tools.
• Treat alignment as a deliverability KPI, not just “SPF pass.”

2) Implement DMARC—and move beyond p=none

DMARC ties SPF and DKIM together, requiring alignment and enabling policy enforcement (none, quarantine, reject) plus reporting [5]. Adoption is rising, yet many domains still don’t enforce protection. One 2025 adoption view notes only 47.7% of domains had DMARC [10]. That gap is also a deliverability gap. DMARC improves trust, reduces spoofing, and provides the data to fix misalignment across business units.

Implementation steps

• Start with p=none to collect reports and map all legitimate senders.
• Fix failures—missing DKIM, misaligned From domains, broken forwarding paths.
• Progress to p=quarantine, then p=reject once confident.
• Route DMARC reports to a monitored mailbox or reporting tool to avoid “set-and-forget.”

Example

A healthcare organization finds that appointment reminders pass DKIM but fail SPF alignment due to a legacy relay. DMARC reporting reveals the culprit, the relay is updated, and the org moves to p=quarantine. Result: fewer phishing lookalikes, fewer user complaints, and improved inbox reputation—especially at providers that weigh trust and complaint rates heavily.

Actionable takeaways

• If you’re still at p=none, set a date to graduate.
• Use DMARC reports as a cross-functional map of “who is sending as us.”

3) Add BIMI to increase brand trust (and reduce mistaken spam reports)

BIMI lets you display a verified brand logo in supporting inboxes, but it depends on strong authentication—typically DMARC enforcement and correct DNS configuration [18]. Beyond aesthetics, BIMI can reduce user uncertainty (“Is this really from you?”), which can indirectly reduce deletions and spam complaints—two behaviors mailbox providers watch closely.

Implementation steps

• Ensure DMARC is enforced (quarantine or reject) and stable.
• Publish your BIMI DNS record and ensure logo format and hosting meet requirements.
• Validate with a BIMI checker and monitor for failures. Research notes a meaningful portion of BIMI records risk display failures due to setup issues [4].

Example

A retail brand runs frequent promotions. Even when messages are legitimate, subscribers sometimes mark them as spam after seasonal spikes. After enforcing DMARC and implementing BIMI, the logo appears in the inbox for supporting providers, reducing “brand confusion.” The team pairs this with preference-center options (Strategy #6), lowering complaint rates during peak sends.

Actionable takeaways

• Use BIMI as a trust amplifier—after you’ve earned it via DMARC.
• Treat BIMI setup like a launch: QA, validate, and re-check after DNS changes.

4) Warm up new domains and IPs with an engagement-first ramp

Mailbox providers don’t “trust” a new sending domain or IP until it demonstrates stable volume, low bounces, low complaints, and strong engagement over time. This is especially critical if you’re launching a new brand domain, migrating ESPs, or separating transactional and marketing streams.

Implementation steps

• Start with your most engaged segment—recent clickers or buyers.
• Gradually ramp volume. Avoid sudden spikes, especially in Q4 when bounces tend to peak [1].
• Keep content consistent and relevant. Minimize list expansion until reputation stabilizes.
• Monitor provider feedback: Gmail Postmaster metrics, bounces, complaints.

Example

A CMO moves marketing sends from a shared to a dedicated domain or subdomain. Week 1: sends only lifecycle messages (welcome, onboarding) to recent opt-ins. Week 2–3: adds newsletters to the top engagement quartile. Week 4+: expands to broader segments once complaint rates remain stable and inbox placement tests confirm improvements.

Actionable takeaways

• A warm-up plan is a revenue protection plan—write it down and follow it.
• Ramp based on engagement, not just time.

5) Control list growth with double opt-in and real-time validation

List quality is reputation. High bounce rates and unknown-user rates quickly erode trust. Validity benchmark reporting put average bounce rates around 1.26% in 2023, with seasonal spikes [22]. Even if your creative is excellent, sending to invalid or low-intent addresses signals poor acquisition hygiene to mailbox providers.

Implementation steps

• Use double opt-in for high-risk acquisition sources—giveaways, partners, paid lead gen.
• Validate emails at capture: syntax + domain + mailbox checks to prevent typos and bots.
• Tag acquisition source and track downstream complaint and conversion rates by source.

Example

A B2C brand scales paid social lead ads and sees deliverability slide within a month. By turning on double opt-in for that source, the list shrinks—but spam complaints drop and click-to-open rate rises. Inbox placement improves because the audience is now self-selected and more likely to engage.

Actionable takeaways

• Treat “cost per lead” and “cost per deliverable engaged lead” as separate metrics.
• Put stricter gates on any source with above-baseline bounces or complaints.

6) Enforce list hygiene with a sunset policy (and automate it)

Continuing to send to unengaged subscribers drags down performance and can increase spam placement—especially as filtering becomes more AI-driven [4]. Validity also notes spam placement pressures rising, underscoring the need to protect reputation by pruning dead weight [1]. A sunset policy formalizes when you suppress or reconfirm inactive addresses.

Implementation steps

• Define inactivity using a metric resilient to privacy changes—clicks, site visits, purchases—rather than opens alone [1].
• Create tiers: 30/60/90/180 days without a click. Adjust by sales cycle.
• Run a re-permission campaign to the “about to sunset” group, then suppress.

Example

A media brand with 500k subscribers has flat CTR and rising spam placement. They suppress anyone with 180 days of no clicks and run a “stay subscribed” campaign to the 120–180 day band. The list shrinks by 22%, but CTR and inbox placement rise because remaining subscribers generate stronger engagement signals.

Actionable takeaways

• Smaller, engaged lists often outperform larger, stale lists in revenue per send.
• Automate suppression rules so hygiene doesn’t depend on heroic manual audits.

7) Write for relevance: segment using SEO + content + social signals

Deliverability is downstream of relevance. When recipients ignore, delete, or complain, reputation drops. Benchmarks show global click-through rates around 3.25% in 2024, with automated and targeted messaging typically outperforming broad blasts [14]. The strategic advantage comes from integrating signals you already have: SEO queries, content performance, and social engagement.

Implementation steps

• Map top organic queries to subscriber intent themes—“pricing,” “templates,” “how-to.”
• Use content analytics to identify topics with high time-on-page and conversion.
• Use social listening and engagement to spot emerging pain points and language patterns.
• Build segments based on observed interest, then tailor subject lines and offers accordingly.

Example

A B2B company sees a spike in organic traffic to “integration checklist” pages and high saves and shares on a related LinkedIn post. They create a segment of subscribers who visited integration content in the last 14 days and send a concise checklist email. Engagement lifts, and subsequent campaigns land more reliably because mailbox providers see consistent positive interactions.

Actionable takeaways

• Use SEO + social language to reduce “this feels irrelevant” reactions.
• Segment by intent signals, not just persona labels.

8) Reduce content-based filtering: keep HTML clean and avoid “spammy” patterns

Modern filters are less about single “trigger words” and more about patterns: deceptive formatting, broken HTML, excessive image-only layouts, and misleading calls to action. Litmus-style measurement guidance emphasizes tracking what truly drives success beyond vanity metrics [11], and clean rendering supports engagement—especially on mobile.

Implementation steps

• Maintain a healthy text-to-image balance. Don’t send image-only emails.
• Use accessible HTML—alt text, logical headings—and keep code lightweight.
• Avoid URL shorteners in bulk campaigns. Use branded tracking domains where possible.
• QA in common clients. Fix broken links and mixed-content issues.

Example

A product launch email uses a single hero image with text embedded, multiple tracking redirects, and a crowded footer. Gmail clips the message; some clients render poorly; clicks underperform. The team rebuilds with live text, fewer redirects, and clear hierarchy. Engagement improves, which then improves inbox placement over subsequent sends.

Actionable takeaways

• Design for scanners—clear text, one primary CTA, fast load.
• Treat rendering QA as deliverability work, not just brand polish.

9) Optimize engagement signals that mailbox providers actually reward

Engagement is not just an outcome—it’s an input to filtering decisions. With Apple Mail Privacy Protection inflating opens (Validity cited open rates reaching 65.1% in 2023 under these conditions), opens alone can mislead optimization [1]. Stronger signals include clicks, replies (for B2B), moving messages to folders, starring, and low complaint rates.

Implementation steps

• Optimize for click-to-open rate (CTOR) and downstream actions, not raw opens [1].
• Build “micro-commitments”: polls, preference updates, “choose your topic” buttons.
• Send from a consistent identity and cadence to train recognition.
• Watch complaint rates. Validity cited spam complaint rates around 0.07% in 2023, with upward pressure in some contexts [22]. Keep complaints well below provider thresholds. Many teams target <0.1%.

Example

A SaaS replaces a generic newsletter with a 3-email sequence based on product-interest clusters. Each email contains one decision CTA (“Choose your use case”). Clicks rise, unsubscribes remain low (Campaign Monitor notes unsub rates typically below 0.2% globally) [41], and deliverability stabilizes because the program generates consistent positive signals.

Actionable takeaways

• Shift reporting to CTOR, conversions, and complaint rate by provider.
• Use interactive choices to create measurable engagement quickly.

10) Monitor deliverability continuously with provider + inbox testing tools

Deliverability needs instrumentation. Validity shows provider variance is real—Gmail deliverability around the mid-80s versus Microsoft inbox rates in the mid-70s in benchmark views [1]. Without monitoring by provider, teams often “optimize blind,” assuming creative is the issue when reputation or authentication is failing.

Implementation steps

• Use Google Postmaster Tools for Gmail reputation, spam rate, and authentication views [83].
• Run inbox placement tests before major launches—seed tests across Gmail, Outlook, Yahoo.
• Track bounce categories (hard vs soft), complaint rates, and authentication pass rates weekly.
• Establish alerting thresholds—bounce rate spikes, sudden Gmail reputation drops.

Example

A CMO sees revenue from email drop while opens look fine (privacy inflation). Postmaster shows reputation deterioration and rising spam rate. Inbox testing confirms Outlook spam placement. Root causes: stale segments and a new vendor added to SPF incorrectly (Strategy #1). Fixes restore placement within weeks.

Actionable takeaways

• Monitor by mailbox provider. “Average deliverability” hides the real problem.
• Build an incident playbook: what you check first when placement dips.

Deliverability Checklist (10-item action plan)

Use this as a weekly or monthly operating cadence:

1. SPF published (single record) and under DNS lookup limits; all senders included [27].
2. DKIM enabled for every sending system; alignment verified [5].
3. DMARC reporting active; roadmap to quarantine or reject defined [5].
4. BIMI implemented and validated after DMARC enforcement [18].
5. Domain or IP warm-up plan documented and engagement-based.
6. Double opt-in enabled for risky sources; capture validation in place.
7. Sunset policy live (click-based inactivity windows) and automated [1].
8. Segmentation driven by SEO + content + social signals to boost relevance [14].
9. Creative QA: clean HTML, accessible text, minimal redirects [11].
10. Monitoring stack: Postmaster + inbox placement tests + alerts [83].

Related questions (FAQs)

What’s an acceptable bounce rate for marketing email?

Benchmarks have placed average bounce rates around ~1.26%, with seasonal spikes [22]. Practically, many teams treat sustained rates above ~2% as a signal to audit acquisition sources and list hygiene.

Do emojis in subject lines hurt deliverability?

Not inherently. Deliverability impact is usually indirect: emojis can affect engagement (positive or negative) and can look spammy if overused. Test by segment and monitor complaint rate and clicks rather than opens alone (informed by engagement measurement guidance [11]).

Is DMARC required for deliverability now?

Provider expectations have tightened, and major ecosystems increasingly expect SPF, DKIM, and DMARC alignment for bulk sending [1]. Even when not strictly “required,” DMARC improves trust and gives you reporting to fix failures [5].

Should we suppress unengaged users even if our list size drops?

Often, yes. Unengaged volume can harm reputation and increase spam placement pressure [1]. A smaller, engaged list usually improves clicks and revenue per thousand delivered.

Make deliverability measurable—and easier to improve

If your team is juggling deliverability across multiple tools, channels, and content sources, consider consolidating insight. At Iriscale, we connect SEO demand signals, content performance data, and social engagement trends to email segmentation and testing—so you send more relevant campaigns that earn better engagement and, over time, better inbox placement.

Our Opportunity Agent scans Reddit conversations for high-intent discussions, recommending blog articles based on real problems your audience is asking about. When you turn those conversations into content, you can then promote that content via email to segments that have already shown interest in related topics—measured by organic search behavior and social engagement tracked in our unified dashboards.

This integrated approach replaces 8–12 disconnected tools (Semrush, Ahrefs, Hootsuite, CoSchedule, etc.), saving $50K–$120K per year in tool costs and eliminating 15–20 hours per week of context switching. Our Knowledge Base preserves strategic context across campaigns, preventing “marketing amnesia” and powering AI-generated content with company-specific intelligence—so every email you send is informed by what’s already working in SEO and social.

Request a demo to see how Iriscale’s deliverability monitoring workflow identifies your fastest wins, or explore our ROI calculator to calculate your tool consolidation savings.

Related guides

• /learn/marketing-automation-best-practices
• /learn/content-workflow-automation
• /learn/seo-content-operations

Sources

[1] https://www.validity.com/wp-content/uploads/2025/03/2025-Benchmark-Report-FINAL.pdf
[2] https://www.validity.com/resource-center/2025-email-deliverability-benchmark-report/
[3] https://www.validity.com/resource-center/state-of-email-march-2025-on-demand/
[4] https://unspam.email/articles/email-deliverability-report/
[5] https://thedigitalbloom.com/learn/b2b-email-deliverability-benchmarks-2025/
[6] https://sales.co/blog/cold-email-deliverability-guide
[7] https://messageflow.com/blog/email-deliverability-2026/
[8] https://www.mailgun.com/wp-content/uploads/pdf/SI-State_of_Email-2024_-_v3_1.pdf
[9] https://selzy.com/en/benchmarks/email-marketing-benchmarks-research-by-industry/
[10] https://martechedge.com/news/litmus-2024-report-reveals-key-email-marketing-trends-and-consumer-insights
[11] https://www.litmus.com/blog/measure-email-marketing-success
[12] https://www.smartinsights.com/email-marketing/email-communications-strategy/statistics-sources-for-email-marketing/
[13] https://designmodo.com/email-marketing-benchmarks-by-industry/
[14] https://www.getresponse.com/resources/reports/email-marketing-benchmarks
[15] https://blog.hubspot.com/sales/average-email-open-rate-benchmark
[16] https://www.brevo.com/blog/email-marketing-benchmarks/
[17] https://mailchimp.com/resources/email-marketing-benchmarks/
[18] https://www.salesforce.com/marketing/email/benchmarks/
[19] https://www.mailgun.com/blog/deliverability/state-of-deliverability-takeaways/
[20] https://www.mailgun.com/state-of-email-deliverability/chapter/introduction/