You can write the perfect email, design it beautifully, and still see it land in someoneʼs spam folder. This is where deliverability comes in.
Deliverability is the measure of whether your emails actually reach the inbox. Itʼs affected by everything from the words you use, to how often you send, to whether people engage with your messages.
In this guide, weʼll look at the most common causes of poor deliverability, what content can trigger spam filters, and practical steps to improve your inbox placement rate.
What Impacts Deliverability #
Email service providers (like Gmail, Outlook, Yahoo, and Apple) use algorithms to decide whether to deliver an email to the inbox, send it to spam, or block it entirely. These algorithms look at several factors:
| Factor | Why It Matters |
| 📈 Engagement | If recipients open, click, or reply to your emails, your domain builds a good reputation |
| ❌ Complaints | If users mark your emails as spam, your future emails are more likely to be filtered |
| 🧹 List hygiene | Sending to old or invalid addresses hurts your reputation. Keep your list clean |
| 🔁 Frequency | Sending too often can trigger throttling, but sending too little can lower engagement |
| 🏷 Content | Words and formatting can trigger spam filters (see below for examples) |
| 🔗 Links & Images | Broken links, tracking-heavy URLs, and image-only emails raise red flags |
| 📥 Spam traps | These are fake addresses used to catch spammers. If you hit one, your emails may be blocked entirely |
Content That Triggers Spam Filters #
Some words, phrases, and formatting choices are more likely to raise suspicion from spam filters. While one or two issues usually wonʼt hurt you, a combination of several can.
| Watch Out For | Examples |
|---|---|
| “Too good to be true” offers | “Earn money fast,” “Get rich today,” “Act now!” |
| Overly urgent language | “Limited time offer,” “Urgent,” “Buy now,” “Don’t miss out” |
| ALL CAPS & too many !!!!!!! | Avoid shouting in subject lines and body text |
| Image-only emails | Always include real text. Don’t rely solely on banners or graphics |
| Suspicious attachments | Don’t include unexpected attachments like ZIP, EXE, or DOC files |
| Link masking or shorteners | Avoid Bitly Connections Platform | Short URLs, QR Codes, and More or similar services if possible. Use clean, branded URLs |
How to Improve Your Deliverability #
Here are the best practices we recommend, especially when sending emails through our platform:
- Write like a human. Avoid robotic marketing language and trigger words. Keep it clear, honest, and relevant.
- Balance images and text. Emails should include both visual content and real, readable text.
- Use clean links. Make sure your URLs are trustworthy and not hidden behind shortened links.
- Test before sending. Always send test emails to different inboxes (e.g. Gmail, Outlook) to see how they behave.
- Avoid attachments. If you need to send a document, link to it instead.
- Warm up your audience. If you haven’t emailed a list in a while, reintroduce yourself gradually instead of sending a full campaign to everyone at once.
Spotting Deliverability Issues #
If you’re seeing low open rates or your emails aren’t arriving, here’s how to investigate
| Symptom | Possible Cause | What to Do |
|---|---|---|
| 📉 Sudden drop in open rates | Spam filtering, reputation issue | Check your content and links, run a spam test |
| 🧊 No engagement at all | Dead or stale list | Clean your list, re-engage or remove inactive contacts |
| 🚫 Emails not arriving | Hard bounces or spam traps | Check for invalid addresses or high bounce rates |
| ⚠️ Consistent Gmail spam | Domain or IP reputation | Check with a tool like Google Postmaster Tools |
Summary #
| Do | Don’t |
|---|---|
| ✅ Send clean, engaging content | ❌ Use spammy phrases or all caps |
| ✅ Include real text alongside images | ❌ Send image-only emails |
| ✅ Test before sending a campaign | ❌ Rely on guesswork or assumptions |
| ✅ Keep your list clean and active | ❌ Blast large cold lists without warming up |
| ✅ Write for people, not filters | ❌ Try to “trick” spam filters with formatting |
Deliverability is about building trust over time. When you consistently send helpful, well-formatted emails to real people who want to hear from you, the inbox becomes your default destination.
