Email Deliverability Issues? Consider These 5 Causes

You can write and design the most amazing marketing emails, but that won’t matter if your subscribers don’t actually see them. Ensuring your emails make it to people’s inboxes (and not the spam folder) is key to any successful email marketing strategy. 

Worried your emails are getting marked as spam? Here are 5 possible reasons your emails aren’t being delivered—and ways to fix them.

1. Your sender domain, IP address, or ESP has a poor reputation.

You could be getting flagged as spam based solely on where you send your emails from, regardless of the content of your emails. 

Email providers like Gmail have certain filters in place to detect probable spam based on your domain, IP address, and email service provider (ESP). Email providers assign a reputation score to sender domains and ESPs based on past instances of spam from those senders. 

If someone using your sender domain (the part of your email address after the @ symbol) or IP address has been flagged as spam, your business could be flagged, too. 

However, changing your domain won’t necessarily fix the issue. Email providers tend to be suspicious of unfamiliar domains, and you’ll need to warm up your domain before they will fully trust you.

The fix: Monitor your reputation with resources like Google Postmaster Tools, and try reaching out to your Domain Name System (DNS) provider to set up authentication measures like SPF, DKIM, and DMARC

2. You’re sending emails to unengaged subscribers.

If the people on your email list aren’t opening, reading, and clicking your emails, email providers may consider your emails spam. Unfortunately, this creates a snowball effect for your emails. Getting sent to the spam folder means even fewer people will engage with your emails, further increasing the chances that you’ll be marked as spam. 

How do you break out of this cycle? One step you can take is to change who receives your emails.

You might be tempted to send all your emails to your entire list. After all, the more inboxes you hit, the more chances of conversions, right? But not all emails speak to all members of your audience. And if a portion of your audience isn’t engaging with your emails, they probably aren’t going to convert, anyway.

The fix: only send emails to “active” subscribers. If someone hasn’t engaged with your emails in the last 90 days, consider them “inactive.” Inactive subscribers require a special approach through re-engagement techniques, and they don’t need to be receiving your broadcast emails.

3. You use too many “spammy” words in your subject lines.

Certain words automatically tip off email providers that you could be a spammer. These words and phrases might be harmless on their own, but they’ve been used by scammers and malicious parties often enough that they set off red flags for spam filters. 

Take a look at your recent subject lines and look out for possible spam triggers like

  • Excessive use of caps lock
  • Overuse of emojis
  • Exaggerated numbers (100%, 0%, #1)
  • False sense of urgency (“once in a lifetime,” “act immediately”)
  • Unrealistic expectations (“Instant weight loss,” “double your income,” “free money.”)


Check out Mailmodo’s list of 284 spam words for a more comprehensive list.

The fix: try writing subject lines without using any of the above triggers, or with just one possible trigger per subject line. Grab your readers’ attention by offering them something they want, not promising them unrealistic or impossible results.

4. Your emails are too image-heavy.

The industry standard for text-to-image ratio is somewhere between 80/20 and 60/40. If your emails are more than 40% images, you could impact your deliverability. 

Spam emails are typically image- and link-heavy, with relatively little text. Even if your emails are totally legitimate, simply resembling a spam email by including too many images can trigger spam filters.

The fix: Lighten up on the images in your emails, and consider A/B testing text-only emails. You might find that your audience prefers plain text instead of graphics and pictures. (We have a whole blog post on that subject here.)

5. You include links that are considered spam.

When it comes to avoiding the spam filter, reputation is everything. Being associated with other websites and domains that have been marked as spam can greatly damage your ability to reach people’s inboxes, and that includes linking to suspicious websites. 

Ideally, your emails should only link readers to your website or social media. After all, the point of your email marketing is to drive traffic to your business. But on the rare occasions you do link people to outside websites (such as recommended partner brands, affiliates, or curated content), make sure those websites are secure.

The fix: Vet all the links you include in your emails. Look for a closed padlock symbol to the left of the URL, and double-check your links are correct when you proofread your emails before sending.


Lost in the alphabet soup of ESP, SPF, DNS, URL, and DMIK? You don’t have to navigate email marketing alone. Schedule a call, and let’s talk about how Sigl Creative can help you optimize your email marketing. There are people out there who want to read your emails—and we want to help you connect with them!

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