Email deliverability

Why are your emails going to spam?

Opens sliding, or a subscriber told you they found you in spam? Here are the five real reasons any email lands in spam or the Promotions tab — and a 30-second test that shows exactly where your next send goes.

Forward a test email here
surfing-barracuda-3011@in.mailtester.ai

Copy
Report in ~30s · one-time address · we never see your list
Not ready? See a sample report first.

Example result: mailtester.ai/report/live

• sara@lisbonletters.beehiiv.com received 14s ago · AI classifier verdict (no real send)
• Deliverability: 62/100
• Verdict: Risky — don't send yet
• Where it lands:
  • Primary: 38%
  • Promotions: 41%
  • Spam: 21%

Emails going to spam: what decides where your send lands

Emails going to spam is a decision made at the receiving end, not at yours. When your campaign arrives, the mailbox provider checks whether the message is authenticated, how people there have treated your mail before, and what the message itself looks like — then files it in Primary, Promotions, or Spam. Your sending platform can't see that decision, which is why a campaign can report every message delivered and still sit in a spam folder. Delivered means the receiving server accepted it. It doesn't mean anyone saw it.

Why do my emails go to spam?

Your emails go to spam for one of five reasons, and they stack: authentication that doesn't line up (SPF, DKIM and DMARC), subscribers who stopped opening, a message that reads like bulk marketing, a sending domain with a thin or damaged reputation, or a send that isn't in spam at all but in Gmail's Promotions tab. Authentication is worth checking first — it fails silently, it's invisible from your side, and it's the only one of the five you can fix once and stop thinking about.

How to fix emails going to spam after a send has gone out

To fix emails going to spam after a campaign has gone out, work backwards from what changed instead of rewriting everything. Check SPF, DKIM and DMARC first: a domain, DNS or sending-platform change is the most common reason a campaign that used to land suddenly doesn't. Then look at who you sent to — a bought, imported or long-dormant segment drags the whole send down, and the fix is to stop mailing the addresses that never open. Resending the same campaign to the same list rarely helps. Fix the cause, then prove it on one email before the next one goes to everybody.

How to stop emails going to spam, send after send

Stopping emails going to spam for good is four habits, not a one-time fix. Publish SPF, DKIM and DMARC once, and keep them correct when you change sending platforms. Mail people who asked for it, and remove the ones who haven't opened in months — inbox providers read that silence as a signal. Keep your volume steady, because a long gap followed by a large blast looks like a hijacked account. And warm a new sending domain up gradually instead of starting at full list size. None of this is fast, and that's the honest part: reputation recovers at roughly the speed it decayed.

Stop emails going to spam: check the email before you send it

The fastest way to stop emails going to spam is to look at the exact message before it goes out, not after. Forward the campaign you're about to send to the test address on this page and you get back where it landed — Primary, Promotions or Spam — whether SPF, DKIM and DMARC lined up on that specific email, a plain-English verdict, and the three things worth fixing first. No account needed for the score. It's the difference between guessing at a subject line and knowing what the filter did with it.

The honest diagnosis

Five things decide where your email lands. Not luck.

Most advice stops at 'clean your list.' Here's the honest version: five signals decide whether any email reaches Primary, Promotions or spam — and you can check every one of them on the exact email you're about to send.

Authentication

• The inbox can't prove the email is really from you: Failed authentication is the most common reason legitimate email lands in spam: if SPF, DKIM and DMARC don't line up, mailbox providers can't confirm the message actually came from you, so they treat it as suspicious and filter it. It's invisible from your side and it fails silently, which is why it's the first thing worth checking.

Engagement

• Too few people open, click or reply: Low engagement tells inbox providers your mail is unwanted: when opens and clicks drop and a handful of people hit 'mark as spam', Gmail and Outlook start routing you to spam to match how your readers behave. A list you bought, imported or grew with a giveaway is the fastest way to trigger it.

Content

• The email reads like a promotion, not a letter: Heavy, promotional content pushes email toward spam and the Promotions tab: lots of links, big images, all-caps subject lines and 'too good to be true' offers read as bulk marketing, not a personal note. On its own it rarely means the spam folder — but stacked on a weak sender reputation, it tips you over.

Reputation

• Your sending pattern looks unreliable: An erratic sending reputation gets you filtered: sudden volume spikes, long silences followed by a big blast, a brand-new or shared sending domain, and mailing addresses that no longer exist all lower the per-domain score that decides whether you reach the inbox. Reputation decays slowly and recovers slowly, so the fix is never 'send more.'

Spam vs Promotions

• Most of the time it's not spam — it's Promotions: The Promotions tab is not the spam folder: most of the time a newsletter that 'vanished' was quietly sorted into Gmail's Promotions tab, where real readers still find it. It's a different problem with a different fix — so before you rebuild anything, find out which one you're actually in.

Find the symptom, find the cause

Spam isn't one problem — it's five, and the fix depends on which one you've got. Start with what you're actually seeing.

“It worked for months, then suddenly everything dropped.”

A sudden drop usually means something changed — a DNS or domain change broke your authentication, a big import tanked your engagement, or a volume spike spooked the filters.

Forward the exact email that's failing to a test mailbox and you'll see which of the five is biting — authentication pass/fail, placement and content, all on your real send.

“It never arrived at all — not even in spam.”

Nothing in the inbox, nothing in Spam, nothing in Promotions usually means the message was never accepted: it bounced, it was blocked, or your platform is still holding it.

That's a delivery failure rather than a filtering problem, and it has its own set of fixes.

“My opens dropped, but nobody says I'm in spam.”

If opens fell but no one's complaining, you're probably not in spam at all — you're in Gmail's Promotions tab, which real readers check but many skip.

That's a content-and-signals problem, not a reputation emergency.

“It only started when I switched to my email platform.”

Every sending platform has its own quirks — shared sending pools on starter plans, growth widgets, imported contacts — that change how the five causes play out.

Why is my email not being delivered?

Start with the bounce, not with your DNS

Almost every refusal comes back to your sending platform with an SMTP status code, and the first digit tells you most of what you need. 5xx is permanent: that server will not accept the message. 4xx is temporary: it's asking you to try again later. Open the campaign's bounce report before you change anything.

• 5xx · Hard bounce: The address doesn't exist, or the server refused you outright
• 4xx · Soft bounce: The mailbox is full, or the server told you to come back later

Two different failures get called the same thing.

If the message reached the mailbox and got filed under Spam or Promotions, it was delivered — it just isn't where you looked, and the five causes above are your list. If it never arrived anywhere, the receiving server refused it or your sending platform is still holding it. That's a delivery failure, and it has its own fixes.