Email Deliverability
Great subject lines, smart send times, and sharp copy do not matter if a message never clears the inbox. Deliverability is the discipline of getting mail past mailbox providers and in front of the people on your list, and it is the foundation every other email metric sits on.
How it's measured: inbox placement rate (IPR), the share of sent email that actually lands in the inbox rather than spam.
See Your Inbox Placement RateWhat Is Email Deliverability?
Email deliverability is whether a message actually reaches a subscriber's inbox, not just whether it left your sending platform. It is easy to confuse with email delivery, but the two measure very different things.
Delivery vs. Deliverability
Delivery simply confirms that a receiving server accepted your message. Deliverability goes a step further and asks where that message ended up: the inbox, the promotions tab, or the spam folder. A campaign can show a near-perfect delivery rate and still perform poorly if a large share of those "delivered" messages never reach the inbox.
How We Measure It: Inbox Placement Rate
Inbox placement rate (IPR) is the percentage of sent email that lands in the inbox rather than spam. It is the clearest signal of whether your program is actually reaching subscribers, and it is the benchmark used throughout the rest of this page. The gap is bigger than most senders assume: roughly one in six emails never reach the inbox at all, even when a sending report shows the message as "delivered."
See exactly where your campaigns are landing, so you can measure true performance and fix what's keeping mail out of the inbox.
Learn MoreHow Mailbox Providers Decide What Reaches the Inbox
Gmail, Outlook, Yahoo, and every other mailbox provider (MBP) act as gatekeepers between your sends and your subscribers. Each one runs its own filtering logic, which is why the same campaign can land in the inbox at one provider and in spam at another.
MBPs Act as Gatekeepers
Before a message ever reaches a subscriber, the mailbox provider evaluates the sender much the way a venue evaluates a guest at the door: checking credentials, watching behavior, and deciding in real time whether to let the message through.
Why Engagement Signals Carry So Much Weight
Opens, clicks, replies, deletions without opening, and spam complaints all feed into how a mailbox provider treats future sends from you. Consistent engagement signals trust; consistent disinterest or complaints signal risk, even if your content and list are otherwise clean.
How Filtering Decisions Get Made
MBPs combine authentication status, sender and domain reputation, content signals, and subscriber engagement history into a single real-time decision. No single factor decides placement on its own, which is why deliverability problems usually require checking several things at once rather than one quick fix.
Why Deliverability Matters
A strong delivery rate can create a false sense of security. A campaign report might show that 97 percent of messages were delivered, but if half of those landed in spam, that number hides a real problem: roughly half your list never had a chance to see the email at all.
Signals a real deliverability problem. Reputation, authentication, or list hygiene issues are likely blocking a meaningful share of sends.
The baseline most healthy, well-maintained email programs should be hitting consistently.
The range top senders reach once authentication, reputation, and engagement are all working in their favor.
What a Low Rate Costs You
Every message that lands in spam instead of the inbox is a message that cannot be opened, clicked, or acted on. Over time, poor placement quietly erodes open rates, click-through rates, and conversions, and it wastes the budget spent creating and sending the campaign in the first place.
How to Check Your Deliverability
Several free and paid tools can show you how mailbox providers currently view your sending reputation and inbox placement.
Sender Score. A free reputation score that benchmarks your sending IPs against industry standards.
Google Postmaster Tools. Shows spam rate, domain reputation, and delivery errors for Gmail specifically.
Microsoft SNDS. Reports IP-level complaint rates and filtering data for Outlook and Hotmail sends.
Feedback loop data. Surfaces complaint signals from Yahoo and AOL recipients.
What Validity Engage Adds
Provider-specific tools each show part of the picture. Validity Engage brings it together in one place, so you can:
Monitor inbox placement across every major mailbox provider from a single dashboard.
Track sender reputation and authentication (SPF, DKIM, DMARC) so issues get flagged before they affect sends.
Check your list for risky or invalid addresses that quietly damage reputation over time.
How Email Delivery Works
Sending an email takes one click, but a message passes through several checks before it ever reaches a subscriber.
The Message Finds Its Route
Your platform hands the message to an SMTP server, which queries DNS to find the recipient domain's mail servers and confirm where it should go.
It Gets Checked and Verified
The receiving provider's Mail Transfer Agent checks authentication, sending IP and domain reputation, and overall sending infrastructure before accepting the message.
The Provider Decides on Placement
Once accepted, the message is counted as delivered. Reputation and subscriber engagement history then determine whether it clears spam filters into the inbox.
Inbox placement rate reflects the combined health of that whole journey: list hygiene and engagement on one side, infrastructure and authentication on the other. Strengthening either side tends to lift IPR over time.
Why You Need Solid Email Infrastructure
Your email infrastructure, the hardware and software you use to send mail, including your IP address and DNS setup, is what proves to mailbox providers that you are who you say you are. A solid infrastructure keeps your sends secure and signals to MBPs that your domain can be trusted.
MBPs rely on authentication protocols to confirm a message actually comes from the domain it claims to come from, which also protects recipients from spam, spoofing, and phishing. Getting these three set up correctly is one of the most direct ways to improve inbox placement.
SPF
Sender Policy Framework traces an email's path from origin to destination, publishing which IP addresses are allowed to send on behalf of a domain. MBPs use it to separate forged mail from legitimate mail.
DKIM
DomainKeys Identified Mail attaches an encrypted digital signature to every message sent. Receiving servers use that signature to confirm the sender is legitimate and the message was not altered in transit.
DMARC
Domain-based Message Authentication, Reporting and Conformance sits on top of SPF and DKIM to stop domain spoofing directly, and tells mailbox providers exactly how to handle mail that fails authentication.
What DMARC Tells Mailbox Providers to Do
The MBP takes no action and delivers the message as usual, even if it fails authentication.
The MBP routes the message to spam or junk instead of the inbox.
The MBP drops the message outright. It is never delivered to the recipient.
A Note on IP Addresses
You can send from a shared IP address, used by multiple senders at once, or a dedicated IP address, used by only you. Since mailbox providers lean on your IP to help judge your reputation, the right choice depends on your send volume, frequency, and how much hands-on management you can take on.
Puts your reputation fully in your own hands, but costs more, needs a proper warm-up period, and only pays off once you are sending consistently large volumes.
More forgiving for lower-volume senders since other senders' good practices help your standing, but their mistakes can drag your reputation down too.
Want a deeper walkthrough of what drives deliverability and how it shapes performance? Grab the guide.
Get the GuideManaging Your Sender Reputation
Mailbox providers lean on your sender reputation to decide how much to trust you. A weak reputation can mean the difference between landing in the inbox, getting routed to spam, or being blocked outright, and a weak reputation shows up directly in your ROI: fewer delivered messages means fewer subscribers who can ever convert. The two biggest levers here are engagement and list hygiene.
List Engagement
How subscribers interact with your mail feeds directly into your reputation. Positive signals, like opening a message, clicking through, replying, forwarding, or rescuing a message from spam, tell mailbox providers your mail is wanted. Negative signals work the opposite way: deleting without opening or marking a message as spam are the clearest signs that your reputation is at risk, and spam complaints in particular do the most damage.
List Hygiene
A clean, current list matters just as much as engagement. Three types of addresses are worth removing on sight:
Invalid or abandoned addresses, often with typos, that drive up your bounce rate every time you send to them.
Addresses that were once real but have since been repurposed by mailbox providers to catch senders with stale, poorly maintained lists.
Addresses that were never real to begin with, created solely to catch senders with careless list-building habits.
A validation step at the point of signup, paired with growing your list organically instead of buying or renting one, keeps these addresses out in the first place. Purchased lists carry real risk: the people on them never agreed to hear from you, you have no way to vouch for the quality of the addresses, and in many regions, including under GDPR, sending to them can mean real regulatory exposure. Repeatedly mailing a dirty, purchased list is one of the fastest ways to end up on a blocklist.
Validity's Contact Data Quality capability keeps your email lists clean so your sender reputation stays protected.
Learn MoreBest Practices to Improve Deliverability
A solid reputation and correctly configured authentication go a long way, but day-to-day sending habits matter too. Mailbox providers weigh these signals when deciding whether a message clears the gateway and where it lands once it does.
Manage Your Sending Volume
New or unfamiliar IPs that suddenly blast out large volumes look exactly like the behavior spam filters are built to catch. Ramp volume up gradually on a new domain, a practice known as IP warming, and spread large sends across a few days rather than all at once, especially around high-volume periods like Black Friday.
Segment and Personalize
Grouping subscribers by behavior and preferences, and tailoring content accordingly, keeps engagement higher. Higher engagement means fewer unsubscribes and spam complaints, both of which feed directly back into your reputation.
Build a Suppression List
Subscribers who never engage are a quiet warning sign to mailbox providers. Grouping inactive subscribers and pausing regular sends to them, aside from an occasional re-engagement attempt, protects your reputation with everyone else. How long to wait before calling someone inactive depends on how often you typically send.
Keep Opt-In Compliant
Confirming that someone actually wants to be on your list, through a double opt-in process, lowers complaints and unsubscribes versus adding people who never explicitly agreed. Encouraging new subscribers to add you to their address book is a simple way to help future sends avoid the spam folder.
Make Opting Out Easy
A clear, one-click unsubscribe link, plus a preference center for subscribers who only want to adjust what they receive rather than leave entirely, reduces frustration and keeps complaint rates down.
Build Brand Recognition
Consistent branding, a recognizable "from" name, and sending from your own domain rather than a free email provider all make it easier for subscribers to trust what they're looking at, which drives the open rates mailbox providers reward with better placement.
Watch Your Subject Lines
All-caps text, excessive exclamation points, and classic spam trigger words draw the same scrutiny from spam filters that they do from subscribers. Descriptive and engaging beats gimmicky every time.
Mind Your Email Body
Heavy use of forms, video, or scripts that not every mailbox provider renders, along with attachments, unoptimized images, missing alt text, a poor text-to-HTML balance, or shortened links, can all trip spam filters or frustrate subscribers who can't read the message properly.
Bringing It All Together
Reaching the inbox is the first hurdle every email program has to clear before anything else about a campaign can matter. That means treating deliverability as an ongoing priority, not a one-time fix, across the technical side (infrastructure and authentication) and the subscriber-facing side (list hygiene, engagement, and brand trust). Keeping an eye on all of it together is what protects your sender reputation and keeps your email program healthy over time.
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