Improve Email Deliverability: 12 Tactics That Actually Work

To improve email deliverability you need to understand what “deliverability” actually means. It’s not just “did the email reach the server” — that’s delivery rate. Deliverability is whether your email reached the inbox versus the spam folder, and whether it was accepted versus rejected at the connection or filtering layer. The gap between the two can be 20–30% of your sends on a poorly managed list.

Here are 12 specific tactics that move the needle, in roughly the order you should address them.

1. Authenticate Your Sending Domain (SPF, DKIM, DMARC)

This is table stakes. As of February 2024, Google and Yahoo require all bulk senders (> 5,000 emails/day to Gmail) to have SPF, DKIM, and DMARC configured. Without them, your emails get rejected or routed to spam at scale.

Authentication tells mailbox providers that your emails are genuinely from your domain and haven’t been tampered with in transit. It’s the foundation everything else sits on.

See our complete guide: SPF, DKIM, and DMARC setup explained.

2. Warm Up New Sending Domains Properly

If you’re moving to DexcyJet from another platform, or setting up a new sending domain, do not send your full volume on day one. Mailbox providers assign reputation scores to new domains — they start at zero and you have to earn trust through consistent, engaged-upon sending.

A cold start on a new domain sending 50,000 emails on day one will result in a significant fraction being spam-foldered or rejected. The correct approach is a 4–6 week warmup ramp.

See the detailed schedule in our post on email warmup for new domains.

3. Keep Your Hard Bounce Rate Below 0.5%

Every hard bounce is a signal that your list has quality problems. Gmail and Outlook track bounce rates per sending IP and domain. Bounce above 0.5–1% regularly and your reputation will degrade.

DexcyJet automatically suppresses hard-bounced addresses. But suppression is reactive — you should also be proactive with address validation at the point of collection. See our full breakdown of email bounce rates.

4. Keep Your Spam Complaint Rate Below 0.08%

Gmail publishes their Postmaster Tools guidelines — sustained complaint rates above 0.1% lead to deliverability problems; above 0.3% leads to rejection. The safe operating zone is below 0.08%.

Causes of elevated complaint rates:

• Sending to people who didn’t explicitly opt in
• Too-frequent sends to an unengaged list
• Content that doesn’t match what the subscriber signed up for
• No easy-to-find unsubscribe mechanism

DexcyJet participates in Gmail and Yahoo’s Feedback Loop programs (where available) and automatically processes FBL complaints as suppressions.

5. Implement One-Click Unsubscribe (RFC 8058)

Since early 2024, Gmail requires bulk senders to support one-click unsubscribe via the List-Unsubscribe-Post header defined in RFC 8058. This lets Gmail show an “Unsubscribe” button at the top of the email — right next to the spam button. Making the unsubscribe button easy to find reduces spam complaints.

DexcyJet adds the List-Unsubscribe and List-Unsubscribe-Post headers automatically on every campaign send.

6. Segment by Engagement Before Sending

This is the highest-leverage deliverability tactic that isn’t about technical configuration. Sending to your entire list regardless of engagement level drags down your average engagement metrics, which mailbox providers read as a signal that your mail isn’t wanted.

Segment your list into:

• Engaged (opened in last 90 days): send normally
• Cold (no open in 90–180 days): reduce frequency, test re-engagement
• Dormant (no open in 180+ days): sunset or remove

See email list segmentation strategies for the full breakdown.

7. Clean Your List Regularly

List hygiene is not a one-time event. It’s an ongoing process. At minimum, quarterly:

• Remove hard bounces (DexcyJet does this automatically)
• Remove chronic soft bounces (3+ consecutive bounces)
• Suppress FBL spam complaints
• Run re-engagement campaigns on cold segments
• Remove anyone who hasn’t engaged in 12 months unless you have a specific reason to keep them

For a detailed protocol, see our post on email list cleaning and hygiene.

8. Check Your Content for Spam Triggers

Spam filters in 2026 are not keyword-based (the days of “FREE!!!” triggering a filter are largely over). Modern filters use machine learning models trained on vast datasets of spam vs. legitimate email. That said, some content signals still matter:

• Image-to-text ratio: Emails that are mostly images with little text are treated suspiciously, because spam has historically used this pattern to evade keyword filters. Aim for at least 60% text by volume.
• Spammy link patterns: Too many links (especially to domains with poor reputation), shortened URLs, or links that redirect multiple times.
• HTML that looks broken: Malformed HTML, mismatched tags, invalid CSS — signs of low-quality or programmatically generated content.
• Excessive punctuation and capitalisation: Still a weak signal, but present.
• Your sending domain reputation: This is the biggest factor. Content matters less if your reputation is strong.

9. Use a Consistent Sending Domain and “From” Name

Inconsistency in your From: headers raises flags. If your subscribers have been receiving email from newsletters@yourcompany.com for six months and you suddenly switch to news@yourcompany.com, you lose the accumulated goodwill of that address’s reputation. The new address starts fresh.

Standardise on one From: address per email type and don’t change it without a migration plan.

10. Avoid Sudden Volume Spikes

Sending 2,000 emails/day for three weeks and then blasting 40,000 on a Friday for a flash sale is a deliverability risk. Mailbox providers’ systems flag sudden volume increases from a given sender as suspicious behaviour.

Plan high-volume sends in advance. If you know a seasonal spike is coming (Diwali promotions, end of financial year), ramp up volume gradually in the weeks before — don’t spike from baseline to peak in a single day.

11. Monitor Your Sender Reputation Proactively

Don’t wait for campaign complaints to find out you have a reputation problem. Monitor continuously:

• Google Postmaster Tools: Domain and IP reputation, spam rate, authentication compliance, delivery errors. Free, and essential.
• Microsoft SNDS (Smart Network Data Services): IP reputation at Outlook/Hotmail. Also free.
• Barracuda Central: Check if your IP is on the Barracuda blocklist.
• MXToolbox: Aggregate blocklist check across dozens of DNSBLs.

DexcyJet’s deliverability dashboard aggregates reputation signals across delivery providers. See DexcyJet’s features for details.

12. Set Up Feedback Loop Registrations

Feedback Loop (FBL) programs notify you when a subscriber marks your email as spam. This lets you suppress the complainant immediately and investigate patterns (which campaign, which segment, which subject line generated the complaint).

Major providers with FBL programs:

• Gmail: Automated via Google Postmaster Tools (volume signals, not individual complaints)
• Yahoo/AOL: Individual complaint forwarding via Yahoo CFL
• Outlook/Hotmail: JMRP and SNDS programs
• SpamCop/Spamhaus: Not FBL, but monitoring these tells you if you’re being listed

DexcyJet handles FBL registration and complaint processing on behalf of accounts using its shared IP pools. On dedicated IP plans, you register your own FBLs through the DexcyJet dashboard.

The Underlying Model

All 12 of these tactics point to the same underlying model: inbox providers are trying to determine whether the people who receive your email want it. Everything that signals “yes, they want it” (authentication, engagement, double opt-in, clean lists) improves deliverability. Everything that signals “no, they don’t” (bounces, complaints, disengagement) hurts it.

For a new sender, start with tactics 1–4 (authentication, warmup, bounce control, complaint control) before anything else. Those are the foundation. Everything else is optimisation.

Try DexcyJet: Real-time deliverability analytics, automatic bounce suppression, RFC 8058 one-click unsubscribe, and 10+ delivery providers for routing and failover. Start free — the infrastructure to ship with confidence.