How to Run a Deliverability Audit: The Complete Checklist for Email Teams

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A deliverability audit is a systematic review of every factor that affects whether your emails reach the inbox. It covers authentication, reputation, infrastructure, content, and list quality. Think of it as a health check for your email sending setup.
Here's why it matters: according to Validity's 2026 Email Deliverability Benchmark, 16.9% of legitimate marketing and outreach emails never reach the inbox. That's roughly 1 in 6 emails going to spam or being blocked entirely. For a team sending 1,000 emails per day, that's 169 emails that prospects never see. Over a month, you're losing more than 5,000 potential touchpoints.
The frustrating part is that most deliverability problems are invisible. Your emails send successfully. Your tool shows them as "delivered." But "delivered" means the receiving server accepted the email, not that it landed in the inbox. The email could be sitting in spam, promotions, or a junk folder. Without a deliverability audit, you have no way to know.
Smartlead built SmartDelivery specifically for this problem. It tests where your emails actually land across major providers and flags issues before they snowball. But whether you use SmartDelivery or run the audit manually, the checklist is the same.
What should you check first in a deliverability audit?
Start with email authentication. Authentication records tell receiving servers that you're authorized to send email from your domain. Missing or misconfigured authentication is the number one cause of deliverability problems, and it's the easiest to fix.
1. SPF (Sender Policy Framework)
SPF tells receiving servers which IP addresses are allowed to send email on behalf of your domain. Without it, any server can claim to be sending from your domain, and receiving servers treat your real emails with suspicion.
What to check:
- Does your domain have an SPF record? (Check with any DNS lookup tool)
- Does the SPF record include all IP addresses and services that send email for your domain?
- Is the SPF record under the 10-lookup limit? Exceeding this limit causes SPF to fail silently.
According to DMARC.org's 2025 Adoption Report, 94% of domains now have SPF records, but 31% of those records have errors that cause partial or complete failure. Having SPF is not enough. Having correct SPF is what matters.
2. DKIM (DomainKeys Identified Mail)
DKIM adds a digital signature to your emails that receiving servers use to verify the email wasn't altered in transit. It proves the email came from your domain and wasn't tampered with.
What to check:
- Is DKIM configured for every service that sends email from your domain?
- Are DKIM keys at least 2048-bit? (1024-bit keys are considered weak as of 2025)
- Are keys rotated at least annually?
3. DMARC (Domain-based Message Authentication, Reporting, and Conformance)
DMARC ties SPF and DKIM together and tells receiving servers what to do when authentication fails: nothing (p=none), quarantine (p=quarantine), or reject (p=reject).
What to check:
- Does your domain have a DMARC record?
- What policy is set? Start with p=none for monitoring, move to p=quarantine, then p=reject as you gain confidence.
- Are you receiving and reviewing DMARC reports? These reports show who is sending email from your domain (including unauthorized senders).
For the complete authentication setup process, see the SPF, DKIM, DMARC complete guide.
SmartDelivery checks all three authentication records automatically and flags misconfigurations with specific fix instructions. No manual DNS lookup needed.
How do you check your sender reputation?
Sender reputation is a score that email providers assign to your sending domain and IP addresses based on your sending behavior. Low reputation means more emails go to spam. It's the single most important factor in deliverability after authentication.
1. Where to check reputation:
- Google Postmaster Tools: Free. Shows your domain reputation with Gmail (High, Medium, Low, Bad) and flags spam rate, authentication success rate, and encryption usage. If you send to Gmail addresses (and you do), this is essential.
- Microsoft SNDS (Smart Network Data Services): Free. Shows your IP reputation with Outlook/Microsoft 365.
- Validity Sender Score: Scores your IP on a 0-100 scale. Above 80 is good. Below 70 is a problem.
2. What damages reputation:
- High bounce rates (above 3%)
- Spam complaints (above 0.1%)
- Sending to inactive addresses
- Sudden volume spikes (going from 100 emails/day to 1,000 in one day)
- Sending without proper warmup
According to Return Path's 2025 Sender Intelligence data, domains with a "High" Google Postmaster reputation have a 95% inbox placement rate. Domains with "Low" reputation drop to 42%. That's the difference between a campaign that works and a campaign that's invisible.
Smartlead's unlimited warmup builds and maintains sender reputation across all connected mailboxes by simulating natural email behavior. The email sender reputation guide covers reputation management in detail.
"We ran a deliverability audit after our open rates dropped from 52% to 19% over two weeks. Turned out one of our sending domains had hit a 'Bad' reputation on Google Postmaster because of a bad list we imported. SmartDelivery caught it immediately. Manual checking would have taken days." - G2 reviewer, email operations lead
How do you check if you're on email blacklists?
Blacklists are databases of IP addresses and domains known for sending unwanted email. If your sending IP or domain appears on a major blacklist, your emails will be blocked or spam-filtered by any receiving server that uses that blacklist.
1. Major blacklists to check:
- Spamhaus (ZEN, SBL, XBL, PBL) - The most influential. Being listed here affects deliverability across most email providers.
- Barracuda Reputation Block List (BRBL) - Widely used by corporate email filters.
- SORBS (Spam and Open Relay Blocking System) - Common in enterprise environments.
- SpamCop - User-reported spam complaints.
2. How to check:
Use a multi-blacklist checking tool (MXToolbox, MultiRBL) to scan your sending IP and domain against 50+ blacklists simultaneously. SmartDelivery includes blacklist monitoring and alerts you if any sending IP or domain gets listed.
3. What to do if you're listed:
- Identify the cause (usually a spam complaint spike or sending to spam traps)
- Fix the root cause before requesting delisting
- Submit a delisting request through the blacklist's process
- Most blacklists delist within 24-72 hours if the underlying issue is resolved
According to Validity's 2026 data, 8% of legitimate commercial senders are on at least one blacklist at any given time. Regular monitoring is essential because blacklist listings can happen suddenly after a single bad send.
Using Smartlead's SmartServers reduces blacklist risk because you're on dedicated sending infrastructure, not shared IPs where another sender's behavior can affect your reputation.
What bounce rate and spam complaint thresholds trigger problems?
Your deliverability audit should include a review of bounce rates and spam complaint rates. These are the metrics that email providers watch most closely when deciding your reputation.
| Metric | Healthy | Warning | Dangerous | Action |
|---|---|---|---|---|
| Hard Bounce Rate | Below 1% | 1-3% | Above 3% | Stop campaign, verify list, remove invalid addresses |
| Soft Bounce Rate | Below 2% | 2-5% | Above 5% | Check sending volume, review infrastructure |
| Spam Complaint Rate | Below 0.05% | 0.05-0.1% | Above 0.1% | Review targeting, reduce frequency, improve relevance |
| Spam Trap Hits | Zero | 1-2 | 3+ | Audit list sources, remove old addresses, reverify |
| Unsubscribe Rate | Below 0.3% | 0.3-0.5% | Above 0.5% | Review messaging and targeting alignment |
Google updated their sender guidelines in late 2024: any domain with a spam complaint rate above 0.1% will see throttled deliverability to Gmail. This threshold is non-negotiable. Monitor it weekly.
Smartlead's SmartProspect provides verified contact data that keeps bounce rates low from the start. Using verified data instead of scraped lists is the single most effective way to prevent bounce rate problems.
How do you test actual inbox placement?
This is the most important step in a deliverability audit because it answers the only question that truly matters: where do your emails actually land?
1. Manual inbox placement testing:
- Create seed accounts across Gmail (personal and Workspace), Outlook (personal and 365), Yahoo, and AOL
- Send your actual campaign email to each seed account from each sending mailbox
- Check where the email lands: Primary inbox, Promotions tab, Spam folder, or not delivered at all
- Repeat for each email variant and each mailbox in your rotation
This is tedious. For a team with 10 sending mailboxes and 3 email variants, that's 30 tests across 6+ email providers. And you need to repeat it regularly because inbox placement changes as your reputation changes.
2. Automated inbox placement testing (SmartDelivery):
Smartlead's SmartDelivery automates the entire process:
- Tests inbox placement across Gmail, Outlook, and Yahoo simultaneously
- Tests from each connected mailbox individually so you see which mailboxes have problems
- Runs tests before campaign launch and on a recurring schedule
- Flags mailboxes with declining placement rates
- Provides specific fixes when issues are detected
According to Validity's 2026 data, teams that test inbox placement before every campaign launch have 28% higher overall deliverability than teams that test quarterly. The difference is catching problems before they affect real campaigns versus discovering them after thousands of emails have already gone to spam.
"We test inbox placement before every major campaign through SmartDelivery. It caught a Outlook placement issue on two mailboxes that we would have missed for weeks otherwise. Those two mailboxes were going 100% to spam on Outlook. We paused them, fixed the DKIM issue, and re-warmed them." - G2 reviewer, outbound sales manager
How do you audit your sending infrastructure?
Your sending infrastructure is the foundation everything else sits on. A deliverability audit should review:
- IP type: Shared vs dedicated Shared IPs mean other senders' behavior affects your reputation. Dedicated IPs give you full control but require proper warmup. Smartlead's SmartServers provide dedicated sending infrastructure so your reputation is entirely your own.
- Number of sending mailboxes: Spreading volume across multiple mailboxes (3+ per domain) reduces per-mailbox volume and looks more natural to receiving servers. Smartlead supports unlimited mailbox connections. SmartSenders automates mailbox setup and rotation.
- Daily sending volume per mailbox: Keep each mailbox below 50-75 emails per day for cold outreach. Going above 100/day per mailbox raises red flags. Smartlead distributes volume across mailboxes automatically.
- Warmup status: Every new mailbox needs 2-4 weeks of warmup before sending campaign emails. Smartlead's unlimited warmup runs continuously on all connected mailboxes, building and maintaining reputation. See the warmup guide for the full process.
- Domain age: New domains (under 30 days) have no reputation. Email providers treat them cautiously. Wait at least 2 weeks of warmup on new domains before any campaign sends.
- Sending patterns: Consistent daily volume builds trust. Sudden spikes (going from 200 to 2,000 emails in one day) trigger fraud detection. Smartlead's SmartAgents manage volume ramping automatically.
How often should you run a deliverability audit?
The audit frequency depends on your sending volume and campaign cadence:
- Before every new campaign launch: Run an inbox placement test through SmartDelivery to verify your mailboxes are placing in the inbox before sending to real prospects.
- Weekly: sender reputation check. Review Google Postmaster Tools and bounce/complaint rates. This takes 5 minutes and catches reputation drops early.
- Monthly: full authentication review. Verify SPF, DKIM, and DMARC records. Check for any changes made to DNS records that might have broken authentication. Scan blacklists.
- Quarterly: comprehensive deliverability audit. Run the full checklist from this guide: authentication, reputation, blacklists, bounces, complaints, inbox placement, and infrastructure. Document the results. Compare against the previous quarter.
SmartDelivery automates most of this cadence. It monitors reputation, checks authentication, scans blacklists, and tests inbox placement on an ongoing basis. The quarterly comprehensive audit becomes a review of SmartDelivery's dashboard rather than a manual process.
According to Return Path's 2025 data, teams that conduct monthly deliverability audits have 34% higher inbox placement rates than teams that audit annually. The difference is catching and fixing problems before they compound.
What is the complete deliverability audit checklist?
Here's the full checklist you can use for every audit. Check each item and note the status:
1. Authentication (check quarterly):
- SPF record exists and includes all sending services
- SPF record is under the 10-lookup limit
- DKIM is configured for all sending services with 2048-bit keys
- DMARC record exists with appropriate policy
- DMARC reports are being received and reviewed
2. Reputation (check weekly):
- Google Postmaster domain reputation is "Medium" or higher
- Validity Sender Score is above 80
- No new blacklist listings
- Spam complaint rate below 0.1%
- Bounce rate below 3%
3. Infrastructure (check monthly):
- All mailboxes are actively warmed up
- Daily volume per mailbox is below 75 for cold outreach
- Volume is distributed across 3+ mailboxes per domain
- No sudden volume spikes in the past 30 days
- Dedicated IPs are properly warmed (if applicable)
4. List Quality (check before each campaign):
- All email addresses verified within the past 30 days
- Hard bounces from previous campaigns removed
- No purchased or scraped lists in the campaign
- Duplicate addresses removed
5. Content (check before each campaign):
- No spam trigger words in subject lines or body
- Text-to-link ratio is reasonable (not more than 2 links per email)
- Unsubscribe link is present and functional
- HTML rendering tested across clients (if using HTML emails)
6. Inbox Placement (check before major campaigns):
- Gmail inbox placement rate above 85%
- Outlook inbox placement rate above 80%
- Yahoo inbox placement rate above 80%
- No mailboxes placing 100% in spam
For the cold email open rate benchmarks 2026, strong deliverability is the prerequisite. All the subject line optimization in the world doesn't matter if your emails land in spam.
Stop guessing where your emails land.
SmartDelivery tests inbox placement across Gmail, Outlook, and Yahoo before you send a single campaign email.
Frequently Asked Questions (FAQs)
1. What is a deliverability audit?
A deliverability audit is a systematic review of every factor that determines whether your emails reach the inbox: authentication records (SPF, DKIM, DMARC), sender reputation, blacklist status, bounce rates, spam complaint rates, inbox placement rates, sending infrastructure, list quality, and email content. It's the diagnostic process for email deliverability problems. Smartlead's SmartDelivery automates most of the audit process.
2. How often should you run a deliverability audit?
Test inbox placement before every major campaign launch. Check sender reputation weekly. Review authentication records monthly. Run a comprehensive full audit quarterly. According to Return Path's 2025 data, monthly auditing leads to 34% higher inbox placement rates compared to annual auditing. SmartDelivery automates the ongoing monitoring so the quarterly audit becomes a dashboard review rather than a manual process.
3. What is the most common cause of deliverability problems?
Poor list quality. Sending to invalid, inactive, or purchased email addresses generates bounces and spam traps that destroy sender reputation. According to Validity's 2026 data, list quality issues account for 43% of all deliverability problems. Use SmartProspect for verified contact data and reverify any list older than 30 days before sending.
4. How do you fix emails going to spam?
Run the full deliverability audit checklist above to identify the root cause. The most common fixes in order of frequency: (1) add or correct DMARC/DKIM/SPF records, (2) warm up mailboxes that have been idle or are new, (3) reduce sending volume per mailbox, (4) clean your list of bouncing addresses, (5) adjust email content to remove spam triggers. Smartlead's unlimited warmup and SmartDelivery address causes 2-4 automatically.
5. What inbox placement rate should I aim for?
Above 85% across Gmail, Outlook, and Yahoo. Industry average is 83.1% according to Validity 2026. Below 75% indicates a significant problem that needs immediate attention. Test placement with SmartDelivery before launching campaigns, not after.
6. Does email content affect deliverability?
Yes, but less than most people think. Authentication, reputation, and list quality have 5-10x more impact on deliverability than email content. That said, certain content patterns do trigger spam filters: excessive links, all-caps subject lines, spam trigger words (FREE, URGENT, ACT NOW), and image-only emails with no text. Keep emails simple: mostly text, 1-2 links, and a clear unsubscribe option.
7. What is the difference between "delivered" and "inbox placement"?
"Delivered" means the receiving server accepted the email. "Inbox placement" means the email landed in the primary inbox (not spam, not promotions, not junk). A campaign can show 99% delivery rate and still have 40% of emails in spam. The deliverability audit focuses on inbox placement because that's what determines whether prospects actually see your emails.
Author’s Details

Rajashree
Rajashree specializes in strategizing and planning B2B SaaS product marketing content. As a writer turned researcher, she has a deep-rooted affinity for writing data-driven content. With over 8 years of experience in the industry, Rajashree has documented her insights in a series of blogs covering genres such as SEO, Content Marketing, Lead Generation, and Email Marketing. Rajashree’s strategic approach and comprehensive industry knowledge make her a trusted authority in creating content that enhances brand visibility and supports business growth.
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Frequently asked questions
What is Smartlead's cold email outreach software?
Smartlead's cold email outreach tool helps businesses scale their outreach efforts seamlessly. With unlimited mailboxes, fully automated email warmup functionality, a multi-channel infrastructure, and a user-friendly unibox, it empowers users to manage their entire revenue cycle in one place. Whether you're looking to streamline cold email campaigns with automated email warmups, personalization fields, automated mailbox rotation, easy integrations, and spintax, improve productivity, or enhance scalability with subsequences based on lead’s intentions, automated replies, and full white-label experience, our cold email tool implifies it in a single solution.
What is Smartlead, and how can it enhance my cold email campaigns?
Smartlead is a robust cold emailing software designed to transform cold emails into reliable revenue streams. Trusted by over 31,000 businesses, Smartlead excels in email deliverability, lead generation, cold email automation, and sales outreach. A unified master inbox streamlines communication management, while built-in email verification reduces bounce rates.
Additionally, Smartlead offers essential tools such as CNAME, SPF Checker, DMARC Checker, Email Verifier, Blacklist Check Tool, and Email Bounce Rate Calculator for optimizing email performance.
How does Smartlead's unlimited mailboxes feature benefit me?
Our "unlimited mailboxes" feature allows you to expand your email communications without restrictions imposed by a mailbox limit. This means you won't be constrained by artificial caps on the number of mailboxes you can connect and use. This feature makes Smartlead the best cold email software and empowers you to reach a wider audience, engage with more potential customers, and manage diverse email campaigns effectively.
How does Smartlead, as a cold emailing tool, automate the cold email process?
Smartlead’s robust cold email API and automation infrastructure streamline outbound communication by transforming the campaign creation and management processes. It seamlessly integrates data across software systems using APIs and webhooks, adjusts settings, and leverages AI for personalised content.
The cold emailing tool categorises lead intent, offers comprehensive email management with automated notifications, and integrates smoothly with CRMs like Zapier, Make, N8N, HubSpot, Salesforce, and Pipedrive. Smartlead supports scalable outreach by rapidly adding mailboxes and drip-feeding leads into active campaigns Sign Up Now!
What do you mean by "unibox to handle your entire revenue cycle"?
The "unibox" is one of the unique features of Smartlead cold email outreach tool, and it's a game-changer when it comes to managing your revenue cycle. The master inbox or the unibox consolidates all your outreach channels, responses, sales follow-ups, and conversions into one centralized, user-friendly mailbox.
With the "unibox," you gain the ability to:
1. Focus on closing deals: You can now say goodbye to the hassle of logging into multiple mailboxes to search for replies. The "unibox" streamlines your sales communication, allowing you to focus on what matters most—closing deals.
2. Centralized lead management: All your leads are managed from one central location, simplifying lead tracking and response management. This ensures you take advantage of every opportunity and efficiently engage with your prospects.
3. Maintain context: The "unibox" provides a 360-degree view of all your customer messages, allowing you to maintain context and deliver more personalized and effective responses.
How does Smartlead ensure my emails don't land in the spam folder?
Smartlead, the best cold email marketing tool, ensures your emails reach the intended recipients' primary inbox rather than the spam folder.
Here's how it works:
1. Our "unlimited warmups" feature is designed to build and maintain a healthy sending reputation for your cold email outreach. Instead of sending a large volume of emails all at once, which can trigger spam filters, we gradually ramp up your sending volume. This gradual approach, combined with positive email interactions, helps boost your email deliverability rates.
2. We deploy high-deliverability IP servers specific to each campaign.
3. The ‘Warmup’ feature replicates humanized email sending patterns, spintax, and smart replies.
4. By establishing a positive sender reputation and gradually increasing the number of sent emails, Smartlead minimizes the risk of your emails being flagged as spam. This way, you can be confident that your messages will consistently land in the primary inbox, increasing the likelihood of engagement and successful communication with your recipients.
Can Smartlead help improve my email deliverability rates?
Yes, our cold emailing software is designed to significantly improve your email deliverability rates. It enhances email deliverability through AI-powered email warmups across providers, unique IP rotating for each campaign, and dynamic ESP matching.
Real-time AI learning refines strategies based on performance, optimizing deliverability without manual adjustments. Smartlead's advanced features and strategies are designed to improve email deliverability rates, making it a robust choice for enhancing cold email campaign success.
What features does Smartlead offer for cold email personalisation?
Smartlead enhances cold email personalisation through advanced AI-driven capabilities and strategic integrations. Partnered with Clay, The cold remaining software facilitates efficient lead list building, enrichment from over 50 data providers, and real-time scraping for precise targeting. Hyper-personalised cold emails crafted in Clay seamlessly integrate with Smartlead campaigns.
Moreover, Smartlead employs humanised, natural email interactions and smart replies to boost engagement and response rates. Additionally, the SmartAI Bot creates persona-specific, high-converting sales copy. Also you can create persona-specific, high-converting sales copy using SmartAI Bot. You can train the AI bot to achieve 100% categorisation accuracy, optimising engagement and conversion rates.
Can I integrate Smartlead with other tools I'm using?
Certainly, Smartlead cold email tool is designed for seamless integration with a wide range of tools and platforms. Smartlead offers integration with HubSpot, Salesforce, Pipedrive, Clay, Listkit, and more. You can leverage webhooks and APIs to integrate the tools you use. Try Now!
Is Smartlead suitable for both small businesses and large enterprises?
Smartlead accommodates both small businesses and large enterprises with flexible pricing and comprehensive features. The Basic Plan at $39/month suits small businesses and solopreneurs, offering 2000 active leads and 6000 monthly emails, alongside essential tools like unlimited email warm-up and detailed analytics.
Marketers and growing businesses benefit from the Pro Plan ($94/month), with 30000 active leads and 150000 monthly emails, plus a custom CRM and active support. Lead generation agencies and large enterprises can opt for the Custom Plan ($174/month), providing up to 12 million active lead credits and 60 million emails, with advanced CRM integration and customisation options.
What type of businesses sees the most success with Smartlead?
No, there are no limitations on the number of channels you can utilize with Smartlead. Our cold email tool offers a multi-channel infrastructure designed to be limitless, allowing you to reach potential customers through multiple avenues without constraints.
This flexibility empowers you to diversify your cold email outreach efforts, connect with your audience through various communication channels, and increase your chances of conversion. Whether email, social media, SMS, or other communication methods, Smartlead's multi-channel capabilities ensure you can choose the channels that best align with your outreach strategy and business goals. This way, you can engage with your prospects effectively and maximize the impact of your email outreach.
How can Smartlead integrate with my existing CRM and other tools?
Smartlead is the cold emailing tool that facilitates seamless integration with existing CRM systems and other tools through robust webhook and API infrastructure. This setup ensures real-time data synchronisation and automated processes without manual intervention. Integration platforms like Zapier, Make, and N8N enable effortless data exchange between Smartlead and various applications, supporting tasks such as lead information syncing and campaign status updates. Additionally, it offers native integrations with major CRM platforms like HubSpot, Salesforce, and Pipedrive, enhancing overall lead management capabilities and workflow efficiency. Try Now!
Do you provide me with lead sources?
No. Smartlead distinguishes itself from other cold email outreach software by focusing on limitless scalability and seamless integration. While many similar tools restrict your outreach capabilities, Smartlead offers a different approach.
Here's what makes us uniquely the best cold email software:
1. Unlimited Mailboxes: In contrast to platforms that limit mailbox usage, Smartlead provides unlimited mailboxes. This means you can expand your outreach without any arbitrary constraints.
2. Unique IP Servers: Smartlead offers unique IP servers for every campaign it sends out.
3. Sender Reputation Protection: Smartlead protects your sender reputation by auto-moving emails from spam folders to the primary inbox. This tool uses unique identifiers to cloak all warmup emails from being recognized by automation parsers.
4. Automated Warmup: Smartlead’s warmup functionality enhances your sender reputation and improves email deliverability by maintaining humanised email sending patterns and ramping up the sending volume.
How secure is my data with Smartlead?
Ensuring the security of your data is Smartlead's utmost priority. We implement robust encryption methods and stringent security measures to guarantee the continuous protection of your information. Your data's safety is paramount to us, and we are always dedicated to upholding the highest standards of security.
How can I get started with Smartlead?
Getting started with Smartlead is straightforward! Just head over to our sign-up page and follow our easy step-by-step guide. If you ever have any questions or need assistance, our round-the-clock support team is ready to help, standing by to provide you with any assistance you may require. Sign Up Now!
How can I reach the Smartlead team?
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