9 Email marketing mistakes to avoid for better results

We’ve been there. And more importantly, we’ve helped a lot of nonprofits and organizations get out of that same rut.

Truth is, email marketing isn’t just about writing a good message. It’s about avoiding the common traps that quietly sabotage your work. Things like broken links, poor timing, or sending one email to everyone without thinking twice.

In this guide, we’re walking through the biggest mistakes we see—plus how to fix them, so your emails actually work. Whether you’re new to email or you’ve been at it for a while, there’s probably a thing or two you could clean up.

Why avoiding email marketing mistakes matters

When email marketing goes wrong, it’s not always loud. You don’t usually see a big red warning sign that says, “This email flopped.” But the signs are there—people stop opening, clicking, or even seeing your emails at all. And over time, all those little slip-ups add up.

Here’s what we’ve seen: mistakes in your email campaigns can hurt your click-through rate, drive up your unsubscribe rate, and damage your sender reputation. That last one is a big deal—if your emails land in the spam folder, it doesn’t matter how good your content is. People won’t even see it.

Every email you send is a chance to build trust, spark action, and grow support. But if things feel off—like the timing is wrong, the design looks broken, or your subject lines miss the mark—you’re not just wasting effort. You’re training people to ignore you.

Avoiding these mistakes isn’t just about doing email “right.” It’s about protecting your impact, your message, and the relationships you’ve worked hard to build. We’ve helped teams turn things around fast by catching these issues early—and now we’ll show you how to do the same.

1. Not planning your email marketing strategy

One of the biggest email mistakes we see? No plan. It sounds simple, but sending emails without a strategy is like building a house without a blueprint. You might get something up, but it won’t hold for long.

We've worked with a lot of teams who were just “winging it.” They’d send out updates here and there, maybe a campaign when something big came up—but there was no rhythm, no big-picture goal. And when results didn’t show up, they didn’t know what to fix.

Start small. Every email campaign should answer a few basic questions:

• Who are we talking to?
• What do we want them to do?
• What’s the goal of this message—clicks, donations, sign-ups?
• How does this fit into our future campaigns?

We always tell our partners: treat your email marketing like a long game. When you map things out ahead of time, you can tell a better story, avoid repeating yourself, and make space for strategy—not just last-minute sending.

Want help building a real email plan that works? We do that too. And it doesn’t have to be complicated—we’ve got frameworks that fit teams of all sizes.

2. Subject lines that hurt your open rates

If your subject line doesn’t grab attention, your email might as well not exist. That sounds harsh, but it’s true. We've seen amazing, thoughtful messages get ignored simply because the subject line didn’t do its job.

Here’s what we’ve learned: the subject line is your first (and sometimes only) shot to get people to open your emails. And there are a few common traps that almost guarantee low open rates.

The big ones?

• Writing subject lines that are too long or confusing
• Using all caps or too many exclamation points
• Sounding like clickbait (people can smell that a mile away)
• Leaving typos or awkward grammar

A lot of folks also forget to test their subject lines. We always recommend A/B testing—even just small tweaks can make a big difference. For example, “Last chance to join us” might perform way better than “Final reminder about the event,” depending on your audience.

Oh—and don’t forget mobile. Most people will see your subject line on a tiny screen. Keep it short, clear, and helpful. Make it obvious why opening your email is worth their time.

We’ve helped organizations go from 10% open rates to 40%+ with just a few small changes to how they write subject lines. It doesn’t have to be complicated—it just has to be clear.

3. Design and layout problems that lower engagement

You don’t need a fancy designer to create a good-looking email—but you do need to avoid the mistakes that make people click away fast.

We’ve seen it a lot: emails that are stuffed with images, take forever to load, or look totally broken on a phone. That kind of layout doesn’t just hurt your click-through rate—it makes people trust you less. If it feels messy or hard to read, they won’t stick around.

Some common design mistakes to watch for:

• Way too many images, or giant ones that don’t load well
• No alt text, which means images don’t show up for screen readers
• Emails that look great on desktop but fall apart on mobile devices

Most folks read email on their phones now, so mobile-first design isn’t a “nice to have”—it’s essential. That means using clear sections, big buttons, and making sure your text is easy to read without zooming in.

We always say: simple wins. Clean layouts, easy-to-scan sections, and one clear call to action usually beat anything flashy. And if you’re not sure how it looks? Send a test to yourself and open it on your phone first.

We’ve helped partners totally refresh their emails just by fixing layout and spacing. It’s not about being fancy—it’s about being clear and easy to read.

4. Sending at the wrong time

Even the best email can flop if it shows up at the wrong time. We’ve seen it happen more than once—great message, solid design, clear CTA… but it lands when people are busy, asleep, or just not paying attention.

Timing matters more than most folks think. Send too early, and it gets buried. Too late, and it’s old news. And if you’re sending without thinking about time zones, you might be showing up at 5 AM or midnight without realizing it.

A lot of partners we’ve worked with used to just hit “send” whenever the email was ready. But once we started helping them schedule based on data—like when their audience usually opens emails—the results changed fast. Higher opens, more clicks, better results overall.

There’s no one perfect time that works for everyone, but here’s what we’ve learned:

• Late mornings midweek (like Tuesday or Wednesday around 10–11 AM) often work best
• Avoid weekends or late-night sends unless your data says otherwise
• Always test—try sending at different times and track what gets the best results

Email timing isn’t something you have to guess at. Look at your past sends, see what worked, and use that info to plan your next move. Small changes here can make a big difference.

5. Common email list management issues

Your email list is kind of like a garden. If you don’t take care of it, things get messy fast. We’ve seen so many teams get stuck because their list was full of bad contacts, outdated info, or folks who didn’t even want to be there in the first place.

One of the biggest mistakes? Buying a list. It might feel like a quick way to grow, but it almost always backfires. These people didn’t choose to hear from you, so they’re more likely to ignore you—or worse, report you as spam. That hurts your sender reputation and makes it harder for the right people to see your emails.

Another common slip-up: sending from a personal email. It seems easier at first, but it looks unprofessional, limits your tracking, and makes it hard to manage unsubscribes the right way.

And speaking of unsubscribes—don’t hide that button. If people want out, let them go. It’s better to have a smaller, engaged list than a big one full of folks who aren’t paying attention.

Here’s what we suggest:

• Regularly clean your list—remove bounced emails, inactive contacts, and duplicates
• Make it easy for people to unsubscribe (it builds trust)
• Segment your list so you’re sending the right messages to the right people
• Use a real email platform, not your personal inbox

When your list is clean and well-organized, everything else gets easier—better results, fewer headaches, and more trust with your supporters.

6. Broken links, missing CTAs, and underperforming content

You can write the perfect email, send it at the right time, and still get no results—just because one link didn’t work. We’ve seen this way too often: a partner sends out a campaign, only to realize the donate button leads nowhere. Or worse, it links to last year’s page.

Broken links aren’t just frustrating for your readers—they kill your momentum. If someone’s ready to act and they hit a dead end, there’s a good chance they won’t try again.

Another mistake we’ve seen? No clear CTA (call to action). Sometimes the message is all info, no ask. Or there’s a button at the bottom, but it’s easy to miss. Every email should make it obvious what you want people to do—click, donate, sign up, share.

To keep your click-through rate strong, try this:

• Test every link before you send
• Use short, clear CTA buttons (like “Give Now” or “Register Today”)
• Don’t overload the email—one main CTA is usually better than three competing ones
• Repeat your CTA more than once if it makes sense

Emails shouldn’t leave people wondering, “What now?” Be clear, direct, and make it easy to take action. A little attention here can go a long way.

7. Neglecting personalization and segmentation

Not every supporter wants—or needs—the same message. But a lot of folks still send the same email to their whole list. We get it. It’s faster. But it’s also one of the most common email marketing mistakes we see.

The truth is, people pay more attention when they feel like you’re talking to them, not just at them. That’s where personalization and segmentation come in.

We’ve seen emails that say “Hi [First Name]” or worse—"Dear First Name Last Name"—because something in the system broke. That kind of mistake doesn’t just look bad. It makes your message feel cold or automated.

Here’s what works better:

• Use first names when you know the info is clean
• Group your list by behavior (like who’s donated, opened past emails, or attended events)
• Send different messages based on what they care about
• Don’t just personalize the greeting—customize the content too

Even simple segmentation helps. If someone’s brand-new, send them a welcome series. If they’re a long-time donor, give them updates on impact. You’re not starting from scratch—you’re building on what you already know about them.

When emails feel personal, people stay engaged. We’ve helped partners do this with tools that make it automatic—and the results are always worth it.

8. Failing to integrate with social media and other channels

Email doesn’t have to do all the work by itself. When you connect it with your other channels—especially social media—you can reach more people, more often, with less effort. But a lot of teams forget this part, and it’s a missed opportunity.

We’ve worked with partners who were posting updates on Instagram, running events on Facebook, and building campaigns through email—but none of it was connected. Their audience had to bounce around and figure it out on their own.

Here’s the better way:

• Add social share buttons to your emails so supporters can spread the word
• Mention your email sign-up form in your social bios and posts
• Reuse your best social content in your newsletters (and vice versa)
• Use engagement from social (like comments or DMs) to build smarter email segments

This kind of integration builds trust. It makes your messaging feel more consistent and less like a one-off. And it helps people stay connected wherever they spend their time.

You don’t need to be on every platform—but you do need to make your channels work together. That way, your message shows up in more places, without more work.

9. Ignoring data and insights from past campaigns

One of the easiest ways to improve your emails? Look at what you’ve already done. But too often, people skip this step. They send something out, hope for the best, and move on to the next one—without checking what worked and what didn’t.

We’ve seen this mistake over and over: teams keep guessing instead of using their own data to guide the next future campaign. That means repeating the same issues, missing chances to get better, and leaving results on the table.

Your email platform likely gives you simple stats—open rates, click-through rates, unsubscribe rate, and more. These aren’t just numbers. They tell a story:

• Did your subject line grab attention?
• Did people click on your CTA or ignore it?
• Did anyone unsubscribe right after opening?

Even a quick glance at your last few campaigns can show patterns. If one email got way more clicks, ask why. If another got ignored, dig into what changed—timing, content, layout?

We always encourage partners to build their next strategy off what they’ve learned. You don’t need to guess what your audience wants—you’ve got clues sitting right in front of you.

Better data = smarter emails. And smarter emails = better impact.

Before you hit send

Most email problems aren’t about effort—they’re about small things slipping through. The wrong subject line, a broken link, bad timing, or sending the same message to everyone… it all adds up.

But here’s the good news: every mistake we covered is fixable. And when you clean them up, you don’t just get better numbers. You build stronger connections, deeper trust, and more impact with every email you send.

If this feels like a lot to manage on your own, you’re not alone. We’ve worked with dozens of nonprofits and teams who felt stuck, unsure, or overwhelmed—until they had the right tools and the right help.

That’s where Harness comes in. We help you simplify your email marketing, clean up what’s not working, and build campaigns that actually drive results. If you’re ready to take email off your plate and do it right, we’re here for you.

Frequently asked questions

How do email design mistakes affect performance?
Design problems—like broken layouts, image-only emails, or unreadable mobile versions—can tank your click-through rate fast. People just won’t engage if your email looks messy or hard to use.

What time should I send emails to get the best results?
It depends on your audience, but mid-morning on weekdays tends to perform well. Try 10–11 AM local time, and always test different times to see what works best for your list.

Why should I avoid using my personal email for campaigns?
It hurts your deliverability, makes your emails look less professional, and gives you zero control over data or unsubscribes. A real email platform helps you stay organized and on-brand.

How can Harness help me avoid email marketing mistakes?
We don’t just give you tools—we give you a team. From planning and design to tracking and support, Harness helps you skip the guesswork and send emails that actually work. We’re like having a fundraising expert and email strategist rolled into one.