A high delivery rate is not a nice-to-have — it is the precondition for your newsletter to exist at all. Land in the spam folder and you are marketing-dead: no opens, no clicks, no revenue. This guide shows how to arrange your technology and strategy so your emails arrive in the inbox — up to date for 2026.

Deliverability is not delivery

Important distinction: your "delivery rate" measures how many emails the recipient server accepted. The actual placement — inbox or spam folder — is the "inbox placement rate". Many tools blur this. You must track both for a full picture.

The three pillars of email authentication

Without correctly configured authentication, you end up in spam at Gmail, Outlook and Apple Mail as of 2024/2025. The three basics:

SPF (Sender Policy Framework)

A DNS TXT record that declares: "these IPs are allowed to send on behalf of my domain."

Example:

v=spf1 include:amazonses.com include:_spf.mailaura.io -all

The -all at the end means "reject everything else" — stricter but safer than ~all.

DKIM (DomainKeys Identified Mail)

Cryptographic signature that proves: "this email was really sent by the claimed sender and has not been tampered with in transit."

In the DNS as a TXT record with a public key. The private key sits in your sending tool.

DMARC (Domain-based Message Authentication, Reporting & Conformance)

Defines what happens when SPF or DKIM fails. Example:

v=DMARC1; p=reject; rua=mailto:dmarc@yourcompany.com

p=reject = failing emails get rejected. Highest protection, also strictest.

Important: since 2024, Google and Yahoo require bulk senders (>5,000 emails/day) to have SPF, DKIM and DMARC configured. Without them, no inbox placement.

Sender reputation: the invisible score

Google, Microsoft and other providers maintain a "reputation score" per sending domain and per IP. This score influences whether future emails land in inbox or spam. The score drops because of:

Hard bounces (non-existent addresses)
Spam complaints
Too fast list growth
Sudden volume spikes
Missing authentication

It rises through:

Consistent sending behaviour
High engagement rates (opens, clicks, replies)
Low complaint rates
Correct authentication
Months of stable patterns

Domain warm-up: the most important start

If you have a new sending domain (or restart), you must not send 50,000 emails on day one. Reputation score would be unstable and the first mailing flagged.

Warm-up plan over 4 weeks:

Week 1: 500/day to highly engaged contacts (your most loyal).
Week 2: 1,500/day
Week 3: 5,000/day
Week 4: 10,000/day, then stepwise to full volume

Mailaura automates warm-up if enabled at setup.

List hygiene: the second most important constant practice

An "old" list is deliverability-deadly. Two practices are mandatory:

Remove hard bounces immediately. Every hard-bounce contact included in future campaigns costs reputation.
Clear out inactives after 6–12 months. Those who have not opened for that long will not start now — but continue to cost reputation in your send list.

Details in Newsletter automation (re-engagement).

Content factors that affect deliverability

Even with correct tech, your content can drop you into spam:

Spam words in subject and body: "FREE", "100 % GUARANTEED", "VIAGRA" etc. (see subject lines post)
A single big image, almost no text: classic red flag because spammers use this to bypass text analysis.
Excessive links: more than 10 links per email increase spam probability.
Broken URL shorteners: Bitly links can be scored suspicious. Use your own tracking domain.
Poor HTML structure: invalid HTML, inline CSS without fallback.

Monitoring and tools

Monitoring pays off. Recommended tools:

Google Postmaster Tools: shows your reputation from Google's view. Free.
Microsoft SNDS: same for Outlook. Free.
GlockApps: inbox placement test across 30+ providers. Paid.
Mail-Tester.com: quick content check per campaign. Free up to 3/day.

Mailaura aggregates Postmaster and SNDS data in one dashboard if you authorise it.

Common deliverability mistakes

1. New domain to a purchased list

Catastrophe. High bounce share + high spam complaints = domain blocked in 2 days.

2. Using a shared IP without warm-up

On shared-IP tools, you share reputation with other senders. Usually works, not always. Good tools (Mailaura, ActiveCampaign) maintain curated IP pools with active bad-sender management.

3. Dedicated IP too early

Many believe their own IP is better. It is — only above 300,000 emails/month. Below, shared IP with good management is always better.

4. Ignoring DMARC reports

DMARC delivers weekly RUA reports on auth failures. Read them. Many marketing teams only discover through this that their domain is being abused by phishers.

Quick check: am I set up well?

SPF record in DNS, verifiable via dig TXT yourcompany.com
DKIM signature active in the tool
DMARC record with p=quarantine or p=reject
Google Postmaster Tools enabled
Hard bounces < 1 %
Spam complaint rate < 0.1 %
Inbox placement rate > 95 % (GlockApps test)
List hygiene: 6+ months inactives cleaned

Conclusion

Deliverability is not an event but continuous discipline. With correct authentication, clean list hygiene, solid content and active monitoring, you stay stably above 95 % inbox placement. With Mailaura you automate most of it — SPF/DKIM/DMARC wizard, automatic bounce cleaning and integrated Postmaster dashboard included.

Email Deliverability: The Ultimate Guide