Email Deliverability
Deliverability vs delivery rate, what Gmail, Outlook and Mail.ru require in numbers, and 9 reasons emails land in spam. + A 15-minute diagnostic checklist.
Email deliverability is the share of emails that actually land in the inbox rather than in spam. It is often confused with delivery rate: a server can accept an email and still file it as spam. Deliverability depends on domain and IP reputation, SPF, DKIM and DMARC authentication, complaints, list quality and the email content.
At the end of this article you'll find a 15-minute diagnostic: 6 checks with benchmarks that show exactly where your emails are getting lost.
At a glance: deliverability in numbers
| Fact | Value | Source |
|---|---|---|
| Average global inbox placement rate | about 84%: one in six emails is lost | Validity, 2024 (via MailReach) |
| Gmail spam complaint threshold | below 0.3%, target below 0.1% | Google, 2024 |
| When Gmail requires SPF, DKIM and DMARC together | from 5,000 emails a day | Google, 2024 |
| When Outlook rejects email without SPF, DKIM and DMARC | from 5,000 emails a day, since May 5, 2025 | dmarcian, 2025 |
| Mail.ru complaint threshold | from 1.1% (up to 10k emails a month) to 0.3% (over 50 million) | Mail.ru |
| Inbox placement of Holymailer mailboxes within limits | 95–99% | Holymailer |
How is deliverability different from delivery rate
Delivery rate answers the question “did the server accept the email?”. Deliverability answers “did a person see it?”.
| Metric | What it shows | Where you see it | Typical trap |
|---|---|---|---|
| Delivery rate | Share of emails that didn't bounce with an error | In any sending tool | A 98% delivery rate says nothing about the spam folder |
| Deliverability (inbox placement) | Share of emails in the inbox | Only via tests and postmaster tools | Sending tools can't see it directly |
If delivery rate is high but opens and replies are low, the problem is almost always deliverability. The emails arrive, but they sit in spam.
How mailbox providers decide where to put an email
A provider checks an email in three layers. A failure at any of them lowers the chance of reaching the inbox.
- Authentication. SPF confirms the sending server, DKIM confirms the email wasn't altered, DMARC ties both to the domain in the From field.
- Reputation. The history of the domain and IP: volumes, complaints, bounces, blocklist listings.
- Recipient behavior. Opens, replies, moves out of spam, deletions without reading and complaints.
Content matters too, but less than people think. Perfect copy won't save a domain with a bad reputation.
What Gmail, Outlook and Mail.ru require from senders
All three require authentication and a low complaint rate. They differ in thresholds and strictness.
| Provider | Authentication | Complaint threshold | Also required |
|---|---|---|---|
| Gmail | Everyone: SPF or DKIM. From 5,000 emails a day: SPF, DKIM and DMARC | below 0.3%, target below 0.1% | PTR record, TLS, one-click unsubscribe for marketing email |
| Outlook | From 5,000 emails a day: SPF, DKIM and DMARC at p=none or stricter | — | Since May 5, 2025, unauthenticated email is rejected |
| Mail.ru | SPF, DKIM and DMARC must all pass | 1.1% to 0.3% depending on volume | Meaningful PTR record, tracking pixel no larger than 1×1, no link shorteners |
Even if you send fewer than 5,000 emails a day, set up all three records: filters take them into account at any volume.
9 reasons emails land in spam
Six of the nine reasons are about infrastructure and the list, and only three are about the email itself.
| # | Reason | How to spot it | What to do |
|---|---|---|---|
| 1 | SPF, DKIM or DMARC missing or broken | Headers show fail or none | Fix the DNS records |
| 2 | New domain or mailbox without warm-up | Spam from the first days of sending | Warm up the mailbox for 3–4 weeks |
| 3 | Sudden jump in volume | A drop right after raising limits | Go back to the previous volume, grow 20–30% a week |
| 4 | Dirty list | Hard bounces above 2–3% | Run the list through a validator |
| 5 | Complaints above the threshold | Data in Postmaster Tools and FBL | Narrow the segment, add a visible unsubscribe link |
| 6 | Domain or IP on a blocklist | Rejections mentioning a blocklist | Fix the cause, request delisting |
| 7 | Cold outreach from the main domain | Regular business email suffers too | Move outreach to separate domains |
| 8 | Link shorteners, attachments, a single image instead of text | Spam on one template only | Remove shorteners and attachments, keep 1–2 links |
| 9 | Identical text in hundreds of emails | Open rate falls on large sends | Personalization and text variations |
Mail.ru warns explicitly: link shorteners that hide the destination page may get your mailing blocked.
How to measure deliverability
No sending tool can see it directly. Use three sources together.
- Placement test (seed test). The email goes to a set of test mailboxes at different providers, and you see which folder it landed in.
- Postmaster tools. Gmail Postmaster Tools shows domain reputation and complaint rate. Mail.ru Postmaster reports statistics by the domain in the DKIM signature.
- Indirect metrics. A sharp drop in open and reply rates with the same list is the first sign of trouble.
Holymailer checks SPF, DKIM and DMARC daily and monitors blocklists for every domain in your dashboard. If a domain gets damaged, replacing it takes a couple of minutes.
15-minute deliverability diagnostic
Run the six checks in order. The first one that fails is your main cause — fix it first.
| # | Check | How | Benchmark | Time |
|---|---|---|---|---|
| 1 | Where the email lands | Send your live template to your own Gmail, Yandex and Mail.ru mailboxes | Inbox at all three | 3 min |
| 2 | Authentication | In Gmail, open “Show original” | SPF, DKIM, DMARC = PASS | 2 min |
| 3 | Blocklists | Check the domain and IP in a blocklist checker | Not on any major list | 2 min |
| 4 | Domain reputation | Gmail Postmaster Tools, Mail.ru Postmaster | Medium or High | 3 min |
| 5 | Complaints and bounces | Campaign stats for the last 7 days | Complaints below 0.1%, bounces below 2% | 2 min |
| 6 | The email | Links, attachments, images, unsubscribe | 1–2 links without shorteners, no attachments | 3 min |
If all six checks pass and emails still land in spam, the issue is usually volume: lower the load per mailbox and spread sending across several mailboxes and domains.
Frequently asked questions
What is a good email deliverability rate?
The global average is about 84% of emails in the inbox, according to Validity's 2024 data. For cold outreach from warmed-up mailboxes, 95% and above is realistic if you stay within limits.
How is deliverability different from delivery rate?
Delivery rate shows how many emails the recipient's server accepted. Deliverability shows how many of them landed in the inbox rather than in spam.
Why do emails go to spam if SPF and DKIM are set up?
Authentication is only the first layer of checks. Most often the cause is reputation: a new domain, a sudden jump in volume, a dirty list or complaints.
How fast does deliverability recover?
After a small drop, in 1–2 weeks of reduced volume and warm-up. If domain reputation has fallen to Bad, it's usually faster and cheaper to replace the sending domain.
Does the email copy affect spam placement?
Yes, but less than reputation. The biggest risks are link shorteners, attachments in the first email and identical text across the whole campaign.
Do I need SPF, DKIM and DMARC if I send fewer than 5,000 emails a day?
Yes. Gmail requires at least SPF or DKIM from all senders, and Mail.ru requires all three. The 5,000 threshold only makes the requirements stricter.
Sources
- Google: Email sender guidelines — in force since February 1, 2024.
- dmarcian: Microsoft Enforces SPF, DKIM, DMARC — Outlook requirements since May 5, 2025.
- Mail.ru: technical and administrative requirements (in Russian).
- Mail.ru: domain statistics in Postmaster (in Russian).
- MailReach: Email Deliverability Statistics — Validity data for 2024.
- Holymailer: how we maintain deliverability (in Russian).
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