Remember Wile E. Coyote?
That relentless desert predator who spent every episode trying to catch the Road Runner? And also failing in the most spectacular ways! He’d order complicated contraptions from Acme Corporation, set up traps, and wait, convinced this time it would work.
But it never did. The anvil would fall on him instead. The rocket would launch him into a canyon wall. The spring-loaded glove would punch him in the face. And off went the Road Runner, with that cheeky “Meep! Meep!”
Wile never realized this: his approach is fundamentally flawed. And no amount of gadgets can salvage his terrible strategy.
A lot of email marketers are just like Wile. They spend hours creating sophisticated campaigns, only to watch them go into spam folders or bounce back. Despite the fancy email templates and latest email marketing tools, their messages struggle to reach their Road Runners. Eroding open rates and poor engagement leave them baffled.
The problem is poor email deliverability. And if you’re making these six big mistakes, your emails are going to crash, just like Wile E.’s plans.
What Is Email Deliverability?
Email deliverability is lauded as one of the biggest email marketing trends in 2025 by experts in this Email Mavlers infographic. That intensifies the focus on strong deliverability for email success.
Email deliverability is the measure of how often your emails get from your server to your subscribers’ inbox. It decides whether or not your prospects will see your email, or if they land straight in the spam folder, or get blocked.
Maintaining high email deliverability should be your utmost priority if you want your emails to remain an effective marketing channel. It directly affects your chances for higher customer engagement and conversions.
The better your email deliverability, the higher the number of your emails reach their intended recipients. Stronger deliverability also means improving your chances of inbox placement for future sends.
Conversely, lower email deliverability stops even the world’s best email campaign from reaching the inbox of the most perfectly targeted audience. Good engagement is out of the question when very few recipients open your emails. And so is brand loyalty and brand recall.
The poor open and click-through rate is most often traced back to a deliverability issue. That’s why you need to pay more attention to the seemingly harmless email practices silently killing your email deliverability rates.
6 Mistakes That Could Be Damaging Your Email Deliverability
Ignoring Sender Reputation
Sender reputation is like a credit history–a record of how well or poorly emails sent from your domain have performed.
If your emails usually get many opens and clicks, very few spam complaints, and hardly any bounces, your sender reputation is strong. You are seen as a trusted sender.
But if people rarely open your emails, don’t click, you get a lot of bounces, or they mark your emails as spam, your sender reputation will take a hit. Inbox providers might start sending your emails straight to the spam folder.
That’s why sender reputation is an important piece of your email marketing strategy. Not taking it seriously will cause serious damage to your email deliverability.
To understand your sender reputation better, keep an eye on your email metrics. If there is a steady decline in open and engagement rates, poor sender reputation could be the culprit.
Using Free Email Domain
Sending marketing emails from free domain email addresses such as Gmail, Yahoo, or Hotmail is a big no-no to avoid fatal effects on your email deliverability. Why?
Free email providers have strict policies to prevent spam. If you send commercial or bulk emails from their domains, they may automatically mark your emails as spam or block them entirely.
Free domains don’t let you set up authentication protocols like SPF, DKIM, or DMARC. These protocols verify your emails are legitimate and not spoofed. Without them, your emails are more likely to be flagged as sus.
Also, emails from free domains have a poor reputation as spammers frequently use them.
Imagine receiving a marketing email from travelagency123@gmail.com. Does it raise questions—Is this a legitimate business? Why don’t they have their domain? Could this be spam or phishing? It does.
Instead, get an email from the same email from info@besttravelagency.com. The custom domain immediately conveys professionalism and trust, making it more likely that recipients will open and engage with the email.
Neglecting List Hygiene
A clean email list is devoid of unengaged, unsubscribed, invalid, or duplicate email addresses. Only engaged, interested, and valid contacts. Meaning your emails will have an easier time reaching your intended recipient’s inbox.
But if you do not purge your email list, chances are you have a large number of problematic contacts that can increase the bounce rate and hurt your sender reputation as well as your email deliverability. Rather, 47.5 % of senders believe the biggest benefit of maintaining list hygiene is improved sender reputation.
One of the best ways to email list cleaning is to send out an email asking your subscribers to update their opt-in preferences.
Not Using Custom Authentication
A large part of email deliverability issues boils down to having been perceived as a spammer in the eyes of spam filters and your recipients. That’s why Google and Yahoo’s latest sender requirements mandate email authentication protocols for all senders.
Email authentication helps mailbox providers verify sending domains and IP addresses as legitimate. This makes it easier to stop email spoofing and help deliver your emails to their inboxes.
Without email authentication, inbox service providers question your legitimacy as a sender. This can send your emails to the spam filters whether you’re actually a spammer or not.
Creating Spam-Triggering Content
If you use tricky or misleading subject lines—like pretending it’s a reply with RE: or a forward with FWD:—or send emails full of typos and poor grammar, you’ll look like a spammer.
The same rings true for certain words or phrases known as spam triggers. Spam filters are on the lookout for these words because spammers use them in scams or junk emails.
If you want to protect or improve your email deliverability rates, please, please do not use spam-flagging language in your email copy and subject lines.
Making Unsubscribe Difficult
Making it difficult for people to unsubscribe from your emails means you keep subscribers on your list who are not interested. That’s way worse than a small email list. They might mark your emails as spam just to stop hearing from you.
Plus, if you don’t include an unsubscribe link, you’re breaking anti-spam laws.
Wrapping Up
Aside from winding up in spam folders, email deliverability issues drastically hamper your ability to maintain healthy subscriber relationships. The good news is that the common reasons for being flagged as spam and that spiral deliverability issues are easy to avoid. The above-mentioned best practices and the ongoing review of your email program are your safety net from deliverability blues.
