13 Things to Avoid When Sending Bulk Emails

Crafting effective emails is crucial, but knowing what to steer clear of is just as important. Here are eleven common mistakes to avoid if you send bulk emails – and you want them to perform.

It’s a miraculous thing if you really think about it. 

You can simultaneously send the same message to anything from 100 people to what amounts to an entire stadium full. You have tremendous power at your fingertips, and your email can make things happen! 

That ability to send people a message that ends up in a place they look at numerous times throughout the day (the inbox) is why email marketing has such a high ROI. 

While everyone knows that the better your emails are, generally the better your results are, there are some things you may need a reminder on. For others who send bulk emails, this may be new knowledge. 

If you avoid these things, you’ll be way ahead of the competition!

1. Sending bulk emails without validating your list

Imagine sending a party invite to a bunch of addresses, only to have half of them bounce back because they don’t exist. Some of the envelopes get marked “Return to Sender,” so you get the invitation back, but the party has already happened. 

Not only is it frustrating, but it also makes you look bad. It’s a waste of time and expense. When you send bulk emails without validating your list, that’s essentially what happens—and it can seriously hurt your sender reputation.

Why list validation is crucial

An email list full of invalid or outdated addresses leads to:

• High bounce rates: Too many bounces can get you flagged as a spammer.
• Lower deliverability: Email providers might start sending your messages straight to spam.
• Wasted effort: Why spend time and money crafting emails that won’t even land in inboxes?

Validating your list ensures you’re reaching real, active recipients who are more likely to engage with your emails. And if you’re sending bulk emails for your business, it’s even more important as bounces can easily pile up.

Tools and techniques for verifying email lists

Email validation tools like ZeroBounce can help you clean up your list by identifying invalid, fake, or risky addresses before you hit “send.” It’s an easy, effective way to protect your reputation and improve your campaign performance.

Integrating an email validation API into any forms on your website makes everything even better. This helps catch typos and fake email addresses at the source, keeping your list clean from the start.

A healthy email list is the foundation of a successful campaign. Validating your addresses isn’t just smart—it’s essential.

Try the ZeroBounce email verifier for free

2. Hitting send without warming up your email

Aside from using a healthy database, there’s another aspect you need to be aware of when sending bulk emails: are you actually ready to send them? 

If you’re about to increase your volume, you may need to warm up your IP and domain first. A sudden spike in your sending behavior may trigger spam filters – and cause your emails to get flagged as spam. 

Warming up your account before you send bulk emails isn’t hard as you can mostly automate it and build your reputation with ISPs gradually and safely. An email warmup tool uses internal email addresses to which it sends emails, then engages with these emails in a way that mimics real-world user behavior. 

For instance, your email warmup tool can engage with emails sent from your domain by:

• Opening
• Clicking links
• Replying 
• Starring
• Marking them as important and not spam

Warming up your IP and domain manually can be tedious and time-consuming. If you want to be in great shape before you start sending bulk emails, consider automating your warmup process – and enhance your reputation. 

Not sure how to warm up your emails? 

Try ZeroBounce Warmup

3. Buying an email list

Buying an email list might seem like an easy way to grow your audience, but it’s a shortcut that leads straight to trouble. Here’s why:

• Low engagement: People on purchased lists didn’t sign up to hear from you, so they’re less likely to open, click, or care about your emails.
• High risk of spam complaints: Sending unsolicited emails can irritate recipients and lead to spam complaints, damaging your sender reputation.
• It’s often illegal: Laws like GDPR and CAN-SPAM prohibit sending emails to people without consent. Ignoring this can result in hefty fines.
• Bad data quality: Purchased lists are usually filled with outdated, invalid, or even fake email addresses, which means higher bounce rates and wasted effort.

Instead, focus on growing your list organically by offering valuable content, incentives, or resources. It might take more time, but the reward is a loyal audience that actually wants to hear from you.

4. Ignoring email personalization

Remember the last time you got a message that started with “Dear Customer”? How did it make you feel? Probably like just another number on someone’s list. That’s why personalization isn’t just a nice-to-have anymore—it’s expected.

These days, people want emails that feel tailored to them. It’s not about knowing everything about your customers; it’s about using the information you have to make them feel seen. Something as simple as addressing them by name or referencing their preferences can make a huge difference.

Take this example:

If you run a clothing store and know someone buys suits and ties regularly, why would you email them promoting women’s formalwear? That’s a quick way to lose their attention—and their trust. Instead, send them content they’ll care about, like a preview of your newest tie collection or a discount on professional wear.

Personalization doesn’t stop there. Think about small, meaningful touches, like sending a birthday greeting with a special discount or celebrating the anniversary of when they joined your email list with an exclusive promo code.

The goal? Even when you send bulk emails, make your recipient pause and think, “Wow, this brand really gets me.” When you do that, you build a relationship.

So regularly ask yourself: “What else can I do to make my emails more and more personal?”

5. Using a misleading subject line

It’s crucial to align your email subject lines with the content in your email’s body. A bait-and-switch email disappoints your customers. It may even anger them. They may decide they no longer trust your brand.

You also run the risk of being flagged as spam. Could you really blame anyone? They may think that since you’re doing something unscrupulous, their only recourse is to hit the spam button. That means they won’t see any more emails you send, but something else happens that can land you in hot water. 

A spam complaint diminishes your sender reputation. Your sender reputation is almost like a credit score for ISPs. A bad sender reputation means you’re likely a spammer, whereas a good one means you’re sending legitimate emails. 

So what’s the takeaway? Even if you aren’t sending spam, you may just be classified as a spammer if you try to mislead your subscribers. If you promise a shirtless photo of a young Alain Delon, you better make good on it.

6. Sending without testing

Do you think the athletes you see in the Olympics are just winging it? No. They’ve gone through the motions. Similarly, a book is not sent to the press without one and usually more proofreaders go through and see if there are any typographical errors or anything unclear.

Before you start sending bulk emails, you want to have a few different eyes on each message. Is it rendering correctly on a mobile phone or a tablet? Someone else should also test the link. 

Imagine if the great email you worked so hard on goes out to tons of people for Black Friday and you are alerted after the fact that one of the most important links was left off? This has happened to many email marketers!

Effective email testing means that you see that everything works and that it also looks good. It’s not just about misspelled words but also about being sure that the email works. 

7. Overloading with images and links

While we’re on the subject of links, sending an email that is jam-packed with links is a bad idea. First of all, you’ll overwhelm your recipient. Secondly, you just may trigger a spam filter.

Related: Email strategist Samar Owais on why your email should have just one CTA

The same could be said about an email that is loaded down with images. First of all, it could take some subscribers more time to download. Just like those emails full of links, they can also trigger a spam filter.

Try to find the right balance between content and design. As Matthew Smith of Really Good Emails explains:  “If your design is in any way too much and it’s actually weighing down your email, then your deliverability goes down.”

8. Not segmenting your audience

Segmenting your email list can make a huge difference, so we will go into some detail here.

Picture this:

You’re throwing a party and inviting everyone you know—friends, family, coworkers, even that neighbor you barely wave to. But instead of sending tailored invites (like a game night for your friends or a fancy dinner for your colleagues), you send one generic message: 

“Come to my thing.” 

What are the chances anyone’s showing up? Probably slim.

The same logic applies to sending bulk emails. If the same message goes out to everyone on your list, it’s like shouting into a crowded room. Some people might care, but most will tune you out.

Benefits of segmenting email lists

Segmenting your audience means breaking your email list into smaller, more specific groups. Why? Because people are more likely to pay attention to emails that feel like they’re meant just for them.

Here’s what you gain by segmenting:

• Better engagement: Emails feel relevant, making people more likely to open and click.
• Lower unsubscribe rates: Your audience won’t feel bombarded with irrelevant content.
• Higher conversions: When your message matches their interests, they’re more likely to take action.

Examples of segmentation strategies

Need help figuring out how to start? Here are some simple ways to break your list into meaningful groups:

• Location: If you’re promoting an event, send invites only to people nearby.
• Purchase history: Reward loyal customers or send tailored recommendations based on their purchases.
• Activity level: Re-engage with subscribers who haven’t opened your emails in a while or reward your most active readers.
• Interests: Use surveys or past behavior to understand what people care about, and tailor content accordingly.

Think of email list segmentation as showing your audience you “get” them. It’s doable, even when you send emails in bulk. Nobody wants to feel like just another name on a list—and when you take the time to make emails personal, it shows. 

Wouldn’t you be more likely to open that email?

9. Ignoring mobile responsiveness

Imagine this: You’re checking your email on your phone—like most people do these days—and you open a message that looks like it was designed for a giant desktop monitor. The text is tiny, you’re pinching and zooming to read, and half the images don’t even load properly.

Frustrating, right? That’s exactly how your audience feels if your emails aren’t mobile-friendly.

Here’s the reality: 61% of consumers open emails on mobile devices. That means if your email doesn’t look good on a smartphone, you lose a huge chunk of your audience before they even read your first sentence.

Best practices for mobile-friendly email design

Making your emails mobile-responsive isn’t rocket science, but it does take some thoughtful adjustments:

• Use a single-column layout: Keep it simple so everything flows naturally on a smaller screen.
• Stick to concise subject lines: Mobile screens cut them off quickly, so make your point early.
• Make buttons easy to click: No one wants to squint and try to tap a tiny link. Use big, bold buttons instead.
• Keep images lightweight: Large images take forever to load on mobile and might not display well.
• Test before sending: Always preview your email on both desktop and mobile to ensure it looks great everywhere.

By taking these steps, you’re respecting your audience’s time and making it easy for them to engage with your message. And when you make things easy, you make things effective.

Related: Mark Robbins of Email Marketing Consortium talks about email accessibility

10. Skipping an opt-out option

Let’s face it—nobody likes to see subscribers leave. But not giving people an easy way to unsubscribe? That’s a fast track to ruining your email reputation. It’s not just bad etiquette; it’s against the law.

The CAN-SPAM Act requires every marketing email to include a clear, easy-to-find way for recipients to opt out. Ignoring this rule can result in fines, not to mention damage to your brand’s credibility. After all, if someone feels trapped on your list, they’re not just unsubscribing—they’re probably complaining about you to others.

So if you send bulk emails, make sure you give people an easy way out.

How to include clear and simple unsubscribe links

Adding an opt-out option doesn’t have to feel like a breakup. Here’s how to do it right:

• Make it easy to find: Place your unsubscribe link in a visible, no-nonsense font at the bottom of your email. Don’t bury it in fine print.
• Use friendly language: A simple “If you’d rather not hear from us, click here to unsubscribe” feels much better than something robotic or guilt-inducing.
• Offer options: Let people choose to reduce email frequency or opt out of certain types of emails instead of leaving entirely.
• Confirm their choice: Send a quick confirmation email to let them know their preferences have been updated.

It might sting a little to see someone go, but respecting their choice keeps your brand trustworthy. And who knows? A graceful goodbye might make them more willing to return in the future.

11. Overwhelming recipients with too many emails

We all know that one person who texts way too much—like, multiple times a day for no reason. You love them, but it’s overwhelming, right? 

The same thing happens with email. If you’re constantly popping into someone’s inbox, even with good intentions, you’re more likely to annoy them than engage them.

Finding the right email frequency is like finding the sweet spot in a conversation. You want to stay top of mind without being overbearing.

Finding the right email frequency

There’s no one-size-fits-all answer, but here are some tips to figure out what works:

• Listen to your audience: Pay attention to your unsubscribe rates and email engagement. A drop in opens or clicks could mean you’re sending too often.
• Offer preferences: Let subscribers choose how often they want to hear from you—weekly, monthly, or only for special announcements.
• Stick to a schedule: Consistency is key. Don’t suddenly switch to daily emails if you promise a weekly newsletter. Let them know what to expect and then follow through with it!

Signs you might be emailing too often

Not sure if you’re overdoing it? Watch for these red flags:

• High unsubscribe rates: If people leave your list in droves, they’re probably overwhelmed.
• Spam complaints: Too many emails can make recipients mark you as spam, even if they signed up willingly.
• Declining engagement: If your open and click-through rates drop, it might be time to back off.

Less can be more when it comes to email. Sending fewer, high-quality messages shows your audience you respect their time—and that’s how you keep them looking forward to hearing from you.

12. Neglecting analytics and feedback

Sending bulk emails without paying attention to how they perform is like shouting into the void. You’ll never know if anyone’s actually listening. If you’re not tracking your email campaigns, you’re missing out on valuable insights that can improve your next email.

Key metrics to track for improvement

Think of analytics as your roadmap to success. Here are the key numbers to keep an eye on:

• Open rate: How many people are actually opening your emails? If it’s low, your subject line might need work.
• Click-through rate (CTR): This tells you how many recipients clicked on a link. A low CTR could mean your content isn’t connecting.
• Bounce rate: Emails that don’t make it to inboxes. A high bounce rate might mean your list needs cleaning.
• Unsubscribe rate: How many people are opting out? If it’s climbing, you might be emailing too often or missing the mark with your content.

These metrics don’t just tell you what’s wrong. They point you toward what’s working so you can do more of it.

How feedback can guide better campaigns

Numbers aren’t the only way to improve. Feedback from your audience is a goldmine for creating emails they’ll actually love. Here’s how to get and use it:

• Ask for opinions: Include a quick survey in your emails or a link to a feedback form.
• Read replies: If someone takes the time to respond to your email, pay attention—you’re getting direct insight into what they value.
• Test and tweak: Use A/B testing to experiment with different subject lines, content formats, or email timing. Let the results guide your strategy.

When you take the time to analyze what’s working (and what’s not), you’re building a smarter, stronger connection with your audience. And that’s a win for everyone.

Here’s what you should never, ever do: not respond to feedback or even a simple reply someone dashed off to you. It’s rude, and it also demonstrates that you don’t understand just how big of a deal someone sending an email is. It’s a big deal when someone decides to contact you. So take the time to write back. 

13. Writing poorly crafted content

No one has time for boring or sloppy emails. If your content doesn’t grab attention or if it feels like an afterthought, it’s heading straight to the trash—or worse, the spam folder.

The secret? Keep it clear, engaging, and to the point. Write like you’re talking to a friend—use language that’s easy to understand and feels relatable. Avoid walls of text by breaking things up with headers, bullet points, or short paragraphs.

And always, always proofread. Typos and grammatical errors can make even the best message look unprofessional. Quality content shows you respect your audience’s time; when you do that, they’re far more likely to engage.

Above all else, keep your bulk emails great

If this is the bonus tip, you’ll have 13 things to avoid. Now we’ll give you one thing you should always do. It’s easier said than done, but keep your emails brilliant. 

Sending bulk emails is about connecting with your audience in a way that feels thoughtful and professional. 

By always avoiding these common mistakes, you’ll be ahead of the pack. Now, you can focus even more on quality, personalization, and strategy.

You’ll not only improve your results but also build lasting trust with your subscribers.