How to Increase Email Deliverability: A Step-by-Step Guide
Deliverability is the foundation of everything in email. If your newsletters don't reach the inbox, nothing else matters. This guide covers the technical and strategic factors that determine whether your emails land in the inbox, the promotions tab, or the spam folder.
Step-by-Step Instructions
Set up proper authentication
Configure SPF, DKIM, and DMARC for your sending domain. These three protocols are now required by Google and Yahoo for bulk senders. SPF tells receiving servers which mail servers are authorised to send from your domain. DKIM adds a cryptographic signature to prove emails haven't been tampered with. DMARC ties them together with a policy for handling failures.
Maintain a clean subscriber list
Remove hard bounces immediately, suppress consistently inactive subscribers, and run re-engagement campaigns quarterly. A clean list means fewer bounces, fewer spam complaints, and higher engagement rates — all of which directly improve your sender reputation. Aim for bounce rates below 2% and spam complaint rates below 0.1%.
Send consistently
Maintain a regular sending schedule without dramatic volume changes. ISPs view sudden spikes in email volume as suspicious — it's a common spam pattern. If you need to increase volume (after a big growth push, for example), ramp up gradually over 2-4 weeks. Consistency builds trust with email providers.
Optimise email content for deliverability
Avoid spam trigger patterns: excessive capitalisation, multiple exclamation marks, spam-associated phrases ('FREE!!!', 'Act now', 'Limited time offer'). Maintain a good text-to-image ratio — don't send image-only emails. Include a plain text version. Keep file size under 100KB. These content factors contribute to your spam score.
Monitor your sender reputation
Check Google Postmaster Tools for your domain's reputation, spam rate, and authentication status. Monitor Sender Score at senderscore.org. Set up alerts for deliverability metric changes. Catching reputation issues early — before they impact inbox placement — prevents small problems from becoming deliverability crises.
Encourage engagement
ISPs increasingly use engagement signals (opens, clicks, replies) to determine inbox placement. Ask subscribers to reply to your emails — this is a strong positive signal. Create content that drives clicks. The more subscribers engage with your emails, the more likely ISPs are to deliver them to the inbox.
Pro Tips
- Use a subdomain for newsletter sending to isolate your email reputation
- Ask new subscribers to add your address to their contacts — this guarantees inbox placement
- Monitor Google Postmaster Tools weekly — it's the most reliable indicator of Gmail deliverability
- If deliverability drops, investigate list hygiene first — it's the most common cause
- Test your emails with mail-tester.com before major sends to catch potential issues
Common Mistakes to Avoid
- Ignoring authentication setup — this is now mandatory for bulk senders
- Sending to purchased or scraped lists — this is the fastest way to destroy deliverability
- Never monitoring sender reputation until a crisis occurs
- Sending inconsistently — long gaps followed by large sends trigger spam filters
- Assuming deliverability is your platform's problem alone — your content and list hygiene matter too
How Aldus Makes This Easier
Aldus handles deliverability proactively. The platform sends through Resend's high-reputation infrastructure, automatically configures authentication when you add a custom domain, processes bounces and complaints in real time, and maintains list hygiene through automated suppression and re-engagement campaigns.
Frequently Asked Questions
What's a good deliverability rate?
Above 95% is considered good, above 98% is excellent. Below 90% indicates serious issues that need immediate attention. Track this metric consistently — a gradual decline is easier to fix than a sudden crash.
Why are my emails going to spam?
Common causes: missing or misconfigured authentication (SPF/DKIM/DMARC), high bounce or complaint rates, poor sender reputation, spam-triggering content, or sending to a list with too many inactive addresses. Check authentication first, then list hygiene, then content.
Does email volume affect deliverability?
Yes. Sudden increases in sending volume trigger spam filters. If you need to increase volume, ramp up gradually — increase by no more than 50-100% per day. Consistent sending patterns at any volume build trust with ISPs.