Email deliverability is whether your message reaches the inbox, not just whether your sending tool accepted it. A campaign can finish with a clean send report while most of it sits in spam. That gap is what this article is about.
Nothing here is a trick. Mailbox providers protect their own users, so they judge senders on evidence. Your job is to hand them the dull, consistent evidence they want.
If you are still working out what to send and to whom, start with our guide to what email marketing is. Deliverability only becomes your problem once mail goes out on a schedule.
Delivered does not mean the inbox
Your sending tool gives you a delivery rate. That figure only means the receiving server accepted the message. Where it went next is a separate decision, taken in a fraction of a second by a filter you cannot see.
So a delivery rate near total is normal, even when nobody reads a word. Bounces tell you an address is broken. They tell you nothing at all about the spam folder.
You therefore have to measure email deliverability indirectly. Opens, clicks, replies and complaints, split by provider, are the signals you actually hold. Read them together, because each one alone is easy to misread.
What mailbox providers actually judge
Filters weigh a few things, and they weigh them per sender rather than per message. Three groups matter most.
Identity, or can they tell it is really you
Anybody can type your company name into the From field. Authentication records prove that a server has permission to send on your behalf. Without them your mail looks like every forgery in the world.
Behaviour, or what people do with your mail
Opens, clicks, replies, and rescuing a message from spam all read as wanted. Deleting without reading reads as tolerated. Pressing the spam button reads as unwanted, and it is the one signal you cannot argue with.
History, or how you have sent before
Steady volume from a steady address builds a record. Sudden spikes, long silences and stale lists all break that pattern. Consequently email deliverability is more about habit than about any single setting.
The three records email deliverability rests on
Three entries in your domain settings do the identity work. Your email platform writes them for you, and somebody then has to add them to the domain.
- SPF lists the servers allowed to send for your domain.
- DKIM signs every message, so any tampering shows.
- DMARC tells a receiver what to do when the first two fail, and where to send its reports.
Set all three up. DMARC is the one people skip, yet it turns the other two into a policy rather than a suggestion. Start it in reporting mode, read what arrives for a few weeks, then tighten it.
The big mailbox providers keep raising what they ask of bulk senders, and each publishes its own current requirements. Check those for the providers your list actually sits on, because the bar moves. If your email deliverability fell off a cliff on one date, an unsigned domain is the first thing to check.
Your sending address matters to email deliverability
Do not send bulk mail from a free mailbox address. The records that prove a sender is genuine sit on the domain, and with a free mailbox that domain belongs to the provider. So your platform has nothing of its own to sign with. Use a domain you own instead.
Many senders also split their streams across subdomains. Marketing leaves from one, receipts and password resets from another. That way a rough campaign cannot drag your receipts down with it, and the messages everybody opens keep a record of their own.
Keep the reply address real and watched. A reply is hard to fake and hard to misread, so it is good evidence that somebody wanted the mail. A no-reply address throws every one of those away.
Shared or dedicated, and why most people should not care
Platforms send either from a pool of addresses shared with other customers, or from one reserved for you alone. Most platforms call the second a dedicated IP. Sales pages make a great deal of this choice.
For most senders the shared pool is better. It carries an established record, and your own volume is too small to build one quickly. A dedicated address suits a business mailing large volumes on a regular schedule, since it needs steady traffic to stay warm.
An occasional sender on a dedicated address gets the worst of both. The record goes cold between campaigns, and every send starts the argument again.
Warming up a new domain or a new platform
A brand new sending domain has no history whatsoever. Ten thousand messages on its first day look much like a spammer who registered yesterday.
Start small and grow slowly. Send to your most recent and most engaged people first, because their opens and clicks are the evidence you need. Then add older groups week by week while you watch complaints.
A worked example, with round numbers chosen to make the arithmetic easy rather than to describe a typical result. Suppose you hold twelve thousand addresses and you spread the warm up over four weeks. Week one goes to the two thousand who opened something in the last month. Week two adds the next three thousand, week three another three thousand, and week four takes the rest. The shape is the point here, and none of those figures is a benchmark.
Changing platform deserves the same patience. Your list has not changed, but the servers behind it have, so the record starts again from nothing.
List hygiene is most of email deliverability
Most email deliverability problems are list problems in a technical disguise.
Old addresses stop existing. Some become spam traps, which providers keep alive precisely to catch senders who never clean up. Others belong to people who signed up once and forgot you entirely.
So drop hard bounces at once. Retire addresses that have ignored you for months, which feels like throwing away reach and really removes dead weight. Never buy a list, and never import the badge scanner file from a conference.
Collecting addresses that behave well is a subject of its own, and we go through it in list building without buying a list. Confirmed opt in loses you some sign ups and removes the addresses that were never going to read anything. When email deliverability is already poor, tightening what comes in stops the problem growing while you clean up the rest.
Hard bounces and soft bounces
A hard bounce means the address does not exist. Remove it immediately, since sending again is how a mailbox provider decides you are guessing at addresses.
A soft bounce means something temporary, such as a full mailbox. Retry a few times, then retire the address once the pattern repeats. Your platform can do this for you if you turn the setting on.
Complaints, and the unsubscribe link
A complaint is somebody pressing the spam button. Unlike a quiet delete, it is an explicit objection, so a filter has no reason to read it any other way. It is also usually avoidable.
People press it when they cannot find the way out. Put a visible unsubscribe link in every message, act on it quickly, and turn on the one click header if your platform supports one. An easy exit protects your email deliverability better than a hidden one protects your list size.
Law sets the footer requirements and the unsubscribe deadline, not the filters. They differ by country, so check what applies where you and your readers sit rather than copying another company's footer.
Frequency matters here too. Mailing far more often than you said you would creates complaints from people who liked you last month.
How content affects email deliverability
Content matters less than most people think, and it has little to do with banned words.
Filters look at the whole picture. A message built as one giant image with a link underneath is hard to read and hard to judge. Spammers lean on link shorteners, so those links arrive carrying somebody else's reputation. A gap between your visible link text and its real destination looks like a trick, because it usually is one.
Plain readable markup, a text version, a footer that says plainly who is writing, and links to your own domain are what you want. There is more on that craft in designing an email that works everywhere.
Diagnosing an email deliverability problem
Work through it in order, rather than changing five things in an afternoon and learning nothing.
| What you see | Usual cause | Where to look first |
|---|---|---|
| One provider drops while the rest hold up | Your record at that provider | Its postmaster tools, if it offers them |
| Everything fell on a single date | A record changed, or a policy did | Recent domain edits and platform notices |
| A new domain never got going | No sending history yet | Warm up pace, since it was probably too fast |
| Slow decline across months | An ageing list | Engagement by age of address |
Then check the dull things. Are the three records still in place after somebody edited your domain settings? Did volume jump? Has a new form started collecting rubbish addresses because nobody put a check on it?
Measuring email deliverability without buying a tool
Split your reporting by mailbox provider. A single average hides the one place where you are in real trouble.
Seed addresses at the main providers give you a rough view of where mail lands. Set a handful up, keep them out of your normal reporting, and read them as a sample rather than a measurement. Some providers also publish a postmaster dashboard for domains they receive mail from. Where one exists, it shows complaints and authentication results you cannot get anywhere else.
Treat the open rate carefully here, since privacy features load images with no human involved. What that number can and cannot tell you fills an article of its own. Clicks and replies are harder to fake, so weight them more heavily when you judge email deliverability.
What is not worth your time
Spam word lists come from an older way of filtering. Writing "free" in a subject line will not sink a healthy sender, and avoiding it will not save an unhealthy one.
Inbox placement scores sold as a single figure are much the same. They squash a per provider, per list picture into one number you cannot act on. Put that money into cleaning the list instead.
Paid audits earn their keep when a genuine problem survives everything above. Usually the answer already sits in your own reporting, unread.
Recovering email deliverability after a bad patch
Recovery runs slower than the fall, and it follows the same path as a warm up. Cut back to the people who still open, send something useful at a steady rhythm, then widen a slice at a time.
Two moves make it worse. Switching platform to escape the problem rarely helps, since reputation attaches to your domain as well as to the servers. Blasting the whole list to see whether things improved simply repeats the send that did the damage.
Expect weeks rather than days. Providers change their mind slowly, which is annoying now and protective later, once your record is good again.
When to bring in help
Ask for help once the three records are right, the list is clean, and mail still fails at one provider.
Take your evidence with you: engagement split by provider, complaint numbers, the dates things moved, and what you changed. Anyone competent can then work on the real problem instead of repeating the checklist you already finished.
Frequently asked questions
What is email deliverability, in plain terms?
It is whether your message reaches the inbox rather than the spam folder or nowhere at all. People confuse it with the delivery rate in their sending tool, which measures something else entirely. Delivery means a server accepted the message. Deliverability means a human could find it afterwards. No report shows the second one directly, which is why you read it from opens, clicks, replies and complaints instead.
Why do my emails keep going to spam?
Usually one of three things. Your domain has no authentication records, so filters cannot tell your mail from a forgery. Your list holds old or bought addresses, which produce bounces and complaints. Or your sending pattern looks erratic, with long silences and sudden spikes. Work through those in that order, because the first is quick and the other two take weeks.
Do I really need SPF, DKIM and DMARC?
Yes, if you send in any volume. SPF names the servers allowed to send for your domain, DKIM signs each message so tampering shows, and DMARC tells receivers what to do when either fails. The big providers publish their own requirements for bulk senders, so check the current list for the ones your readers use. Start DMARC in reporting mode, read what comes back for a few weeks, then tighten the policy.
How long does warming up a new domain take?
Plan for weeks rather than days. Begin with the people who opened something recently, since their behaviour is the evidence a provider wants. Add older groups gradually while you watch complaints and bounces. If either climbs, hold at that volume until it settles instead of pushing on. Moving to a new platform needs the same patience, because the servers behind your list have changed.
Does buying a list hurt email deliverability?
Yes, and faster than most people expect. Bought lists carry dead addresses and spam traps, which providers keep alive specifically to catch senders who never clean up. The complaints arrive quickly, because nobody on that list asked to hear from you. One bought list can undo months of careful sending, and the recovery takes longer than the campaign was ever worth.
Should I delete people who never open anything?
Retire them, yes. An address that has ignored you for many months is not reach, it is dead weight that drags your record down. Try one short re-engagement message first, then let the quiet ones go. Your list gets smaller and your results usually improve, because the people left actually want the mail.
Do spam words in the subject line matter?
Far less than the old advice suggests. A filter is mostly judging the sender, so one word in a subject line will not decide where a healthy sender lands. Subject lines still matter, but by a different route. A dull subject gets ignored, and being ignored week after week is exactly the behaviour that weakens email deliverability over time. So write the subject to earn an open, not to dodge a word list.
How can I tell where my emails are actually landing?
Not from your own inbox, which is the test most people try first. You are an engaged reader of your own mail, on a device that already has the address in its contacts, so it lands well for you and proves nothing about anyone else. Split your reporting by mailbox provider instead. Then compare providers against each other rather than against a target, because one that used to look like the rest and now does not is the thing worth chasing.
How long does it take to fix email deliverability?
Technical faults clear quickly, and a missing record can be right within a day. Reputation takes weeks, because providers change their mind slowly and only after watching you behave. Cut back to engaged people, send something useful on a steady rhythm, then widen a slice at a time. Email deliverability recovers in the same shape as a warm up, which is why rushing it usually starts the fall again.