Content
Mistakes in Email Campaigns: 10 Examples That Cost You Money and Customers
April 3, 2025
12 mins
Are your emails not being opened, with clients unsubscribing in droves and your offers going unnoticed? It could be due to poor subject lines, incorrect segmentation, or intrusive content. Even worse—if your emails aren’t reaching recipients at all or are ending up in spam.
In this article, the Promodo team discusses the most common mistakes in email campaigns and provides specific solutions to help avoid losses and make your campaigns more effective.
If a client isn’t opening your email, it means the campaign isn’t working. Let’s look at the most common mistakes in promotional emails, trigger emails, newsletters, and more.
An undefined target audience and lack of segmentation result in sending the same email to all subscribers. This mistake harms performance: many people receive irrelevant content and lose interest. In contrast, narrowly targeted and personalized emails always yield higher open rates and clicks.
For example, a company sends the same discount email for sportswear to all clients. Part of the audience, who’s only interested in electronics, will consider this email spam. A few bad experiences, and users will start avoiding your emails or even unsubscribe.
Segmentation would have helped retain this user, and personalization would have led to conversions.
The subject line is the first thing a recipient sees in their inbox. If it’s uninteresting, non-informative, or too generic, the email gets ignored or deleted. Using trigger words like “Free,” “Urgent,” “You’ve won!,” or excessive exclamation marks looks suspicious—recipients often send such emails to spam. This harms your sender reputation, both with recipients and algorithms.
For example, an email with the subject “SALE!!! DISCOUNTS!!! BUY NOW!!!!” will almost certainly end up in spam or be ignored—it looks like mass advertising and doesn’t offer real value. Additionally, excessive use of capital letters may come across as aggressive marketing and breed distrust. Using no more than 20-30% uppercase letters in the subject is recommended to avoid visual overload and avoid triggering spam filters. A better option could be: “Hot discounts this week – don’t miss out!”
Instead of a technical phrase, insert a mini-preview of the email content, such as: “5 books to read this spring.” This increases the chances that the email will be noticed and opened, as it immediately highlights its value to the recipient.
If every email looks like a direct advertisement or constantly pushes a purchase, subscribers will quickly lose interest.
Emails that offer nothing but “buy from us” tend to have low engagement. Moreover, sending only promotional messages can reduce trust and even harm your sender reputation, as an overload of sales-driven emails might trigger spam filters.
For example, imagine a customer subscribes to a bookstore’s newsletter expecting book recommendations, curated selections by genre, author interviews, or exclusive discounts. Instead, they only receive emails like “Today Only: 10% Off All Books!” or “Shop Bestsellers at a Discount.” No personalized picks, no reviews—just repeated sales pushes. After a few such emails, the customer starts seeing the brand as just another store pushing products without added value. As a result, they stop opening emails and eventually unsubscribe.
Email marketing isn’t just about immediate conversions—it’s about building relationships with your audience. Balance promotional offers with genuinely interesting and useful content, such as industry news, tips, reviews, and case studies.
A massive block of unstructured text can overwhelm readers. Most people skim their emails quickly—if they see a never-ending wall of text, they might think, "I’ll read this later" (but in reality, they never do). Trying to pack too much information into one email dilutes the main message.
For example, imagine a company sends a weekly blog digest, but instead of short previews, they paste full articles into the email. The result? A ridiculously long email spanning multiple screens. The reader opens it, scrolls a bit, and then closes it—too much effort to read it all.
Another common mistake: a promo email listing ten different products in tiny text with no visuals. The reader gets lost, unsure what the email is even about.
Keep it clear and concise. Every email should have one main focus—whether it's a key message, offer, or topic. Structure matters! Use headings, bullet points, and visuals to make the content easy to scan and digest.
Even the best email content can be ruined by technical issues. These "small details" actually have a huge impact on user experience.
Your email might be fantastic, but if it’s hard to read on mobile or the visuals don’t load properly, people will close it without a second thought. Mobile optimization is a must!
For example, imagine a promo email with a big banner saying “50% OFF” and a call-to-action button. It looks perfect on a computer, but on a phone, the image is too small, the text is unreadable, and the button is hard to click.
Another common issue: banners displaying incorrectly due to improper sizing or lack of responsive design. Always test your emails across different devices and in Dark Mode to ensure a seamless experience for all users.
Take a look at how Promodo’s digests are optimized for mobile devices and adapted for dark mode 👇
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To avoid these issues, always test and preview your emails before sending them out to a large audience.
Also, don’t forget about dark mode! Many users have it enabled, so make sure your logo, text, and images look good on a dark background. Test how text colors and buttons appear in Dark Mode to ensure readability and a polished design.
Email frequency matters a lot. If you bombard subscribers with daily emails (or even multiple times a day), they will quickly start ignoring them or unsubscribe altogether.
Every brand, company, offer, and audience is different, so the optimal email frequency varies. You can take it a step further by adapting the frequency for segmented groups—some may appreciate frequent updates, while others prefer only the most important emails.
Email fatigue is real. Too many promotional emails can irritate subscribers and lower engagement. For example, an online store might send emails every day during Black Friday week and then twice a day as the sale ends. Even discount-hungry subscribers can feel overwhelmed, leading them to ignore or unsubscribe.
On the flip side, emails that are too rare or irregular (e.g., once every few months without consistency) make subscribers forget about you. Someone might sign up for a newsletter expecting useful tips but receive an email only once every two months. When they finally get an email, they may not even remember signing up and unsubscribe due to a lack of relevance.
Every marketing email should have a clear goal—what action do you want the recipient to take? If this action isn’t clearly defined or highlighted in the email, engagement drops significantly. Readers should immediately understand what to do next. Without a strong call to action (CTA), they might just close the email without taking any steps.
Your email should guide the recipient toward a specific action—visiting your website, using a discount, signing up for a webinar, etc.
For example, saying, “We have some new arrivals, check them out if you’re interested” is too vague and uninspiring. Instead, be direct and exclusive: “Be the first to explore our latest collection—click here to see what’s new!”
On the flip side, too many CTAs in one email can be just as harmful. If subscribers are overwhelmed with multiple actions, they may end up doing nothing at all. Both extremes hurt conversion rates.
For example, at the end of Promodo’s digests, we include two types of CTAs: one for readers who want to explore more content and another for those ready to connect directly with our sales team. 👇
A clear and noticeable CTA directly affects click-through rates and conversion. As a result, each email should provide the reader with a clear answer to the question: "What should I do next?" and motivate them to take that action.
Sending a newsletter without checking it is a risky move. Small mistakes happen to everyone: a typo might sneak in, an image might display incorrectly, a link may not work or lead to the wrong place. If these issues aren't caught before sending, your reputation suffers, and sometimes one technical mistake can completely derail your sales.
For example, an incorrect promo code or a “dead” link to a product will nullify your entire promotional campaign. Similarly, untested trigger emails might be sent out incorrectly (double sends, mixed-up names, etc.).
“Do not launch mass sending until you’re sure everything works as intended. At a minimum, proofread the text (ideally, have someone else from the team do it — a fresh set of eyes will catch mistakes more easily), and check the spelling. You can also send a test email to yourself and your colleagues.
Make sure the design looks correct on different devices, all images load properly, and the links open and lead to the correct pages. Ensure that the sender’s field and the subject line display correctly (without random symbols or mistakes)”.
Svitlana Fursa, Head of Retention Marketing at Promodo
Triggered (automatic) emails are messages sent in response to a user action or event (such as registration, abandoned cart, subscription anniversary, etc.). If you haven't set up such scenarios, your interaction with the audience might be untimely or insufficiently relevant.
On the other hand, improper use of automation (e.g., sending emails from a “no-reply” address or poorly thought-out workflows) leads to decreased engagement. People don’t like interacting with robots: an email from “[email protected]” feels like a dead end since there’s no way to respond.
Additionally, there are cases when a user registers on the website but doesn't receive a welcome email or instructions—this is a poor start, as the customer may feel lost about what to do next.
Another common mistake is when an online store sends abandoned cart emails but does so without personalizing the products. The likelihood of the recipient completing the purchase decreases significantly.
“For products with a long decision-making cycle (electronics, furniture, clothing) – it is recommended to send the first reminder after 1-2 days to give the user time to think and offer an additional incentive (discount, free delivery, etc.).
For impulse purchases and quick decisions (e.g., online food delivery) – the reminder should be sent within 30-60 minutes after the cart is abandoned, as the customer is likely to place an order elsewhere after a few hours”.
Svitlana Fursa, Head of Retention Marketing at Promodo
Track the performance of automated emails just like regular ones: if you notice that welcome emails are rarely opened, it might be worth improving the subject line; if cart abandonment reminders aren’t working, test different content or timing. Properly implemented automation helps nurture leads and maintain contact with customers without additional effort, while making communication more personalized and timely.
Another critical mistake is not paying attention to whether your emails even reach the inbox. You can perfectly execute all the creative aspects, but if the email ends up in the spam folder, the effect is null.
Often, senders unintentionally harm their sender reputation. For example, using "spammy" words, overly aggressive subject lines, or sending emails without the recipient's consent leads to complaints and marking your emails as spam. A few of these signals, and your future mailings will be automatically filtered.
Also read our article Why Emails End Up in Spam and How to Avoid It.
Technical settings are just as important: if you haven’t configured domain authentication, email services may not trust your messages. Email authentication shows servers that your emails come from a trusted source.
A few important points:
The listed mistakes are common even in popular mailings. It’s important to regularly review your strategy and approach: analyze what can be improved in your emails, test new ideas, and take into account feedback from your audience. By learning to avoid these mistakes, you’ll elevate the effectiveness of your email campaigns to a new level and achieve better results from this communication channel.
Personalization and segmentation are top strategies in email marketing, so they deserve special attention.
Use the features of your email campaign service—most services allow filtering subscribers by tags, location, activity, etc. Platforms like HubSpot or eSputnik offer advanced segmentation with automatic list updates and CRM integration. This allows you to create dynamic content that places different blocks in the email depending on the segment or behavior of the recipient (for example, different product recommendations for different segments).
These tools can even predict who and when to send the email to (predictive segmentation) and contain libraries of pre-made segments for typical scenarios.
Important: Don’t forget to regularly review segment settings and update personalized content to keep it relevant.
The content of the email must be valuable to the recipient and well-designed. It's also important to think about the benefit to the reader: exclusive content, useful tips, personalized offers.
It all starts with the subject line—it should grab attention and reflect the content. Experiment with the style: sometimes a concise subject works better, sometimes an intriguing question. Be sure to write a preheader (the first few lines of text visible in the email preview)—it complements the subject and increases the open rate.
In the email itself, present the information in a structured way: use subheadings, bullet points, and bold for key ideas so that the reader can easily "scan" the text. The design of the email should be simple and on-brand: include the logo, stick to your brand colors, but avoid cluttering the layout. Images and graphics should complement the text, not replace it. Ensure that each email displays correctly on mobile devices, as nearly half of opens come from smartphones.
A responsive HTML template is a must-have: check that the text is readable, the spacing and fonts display correctly, and the CTA buttons are large enough for a finger click.
“Interactive content is actively used in emails today to increase recipient engagement. This can include dynamic elements based on AMP for Email, such as surveys, product or offer carousels, or forms for responding directly within the email. Additionally, gamification without AMP, such as quizzes, mini-games, word searches, or other creative mechanics, can be incorporated. Using interactive elements helps make the email more engaging and increases the likelihood of interaction with the brand”.
Svitlana Fursa, Head of Retention Marketing at Promodo
Automated workflows save time and improve the efficiency of email campaigns. Classic examples include welcome series for new subscribers (a series of introductory emails gradually familiarizing them with products), and trigger-based emails based on behavior (e.g., abandoned cart reminders, birthday emails with discounts, re-engagement emails for inactive users).
A well-thought-out sending timing means sending emails when the subscriber is most likely to open them. Analyze open rates and click-through data to choose the optimal time.
You can also set up sequences that guide leads from the first contact to conversion (lead nurturing), automatically moving them between segments, i.e., changing the category they belong to and adjusting the communication accordingly.
The main idea: automation allows you to move leads through the sales funnel without requiring manual intervention from managers. Each subsequent email is sent based on what the person has already done (or not done), and the system automatically adjusts their segment and selects appropriate content. This significantly increases the efficiency of email campaigns and conversion rates.
For large e-commerce projects, it’s worth setting up triggers for all key events: from abandoned cart series to follow-up emails (such as feedback requests, related product recommendations, etc.).
It’s impossible to perfectly predict the audience’s preferences from the start, so A/B testing should be an integral part of your strategy. Test different elements of the email step by step: subject lines, preheaders, sender’s name, content, calls to action, template design, and send time.
Change one element at a time and send two versions of the email to two subgroups of your segment in equal proportions. Based on the results (open rates, clicks, conversions), determine which version worked better.
But it’s important: don’t just compare differences of 5% or 10%. You need to consider the statistical significance of the results. Small sample sizes or too short test periods can lead to skewed data. So, before making decisions, ensure the results are statistically significant.
What to do if your database is small?
Thus, A/B testing becomes not just an experiment but a methodical and effective part of your email strategy. Optimization is a never-ending process: analyze, draw conclusions, and try new ideas. This allows you to gradually refine each aspect of your email campaigns and improve their performance over time.
Pay special attention to testing subject lines and calls to action, as they most significantly impact open rates and clicks. If resources allow, consider testing not only individual emails but entire email series and funnels. For instance, try different numbers of emails in a welcome series or different touch frequencies, and see which combination provides the best conversion to sales. Always balance innovation with proven solutions: reinforce successful findings, but always leave room for new ideas.
No campaign can be effective without thorough analysis of metrics and tracking open rates. Monitor the main indicators for each campaign: open rate, CTR (click-through rate), conversion rate (if the email aims for a specific action), unsubscribe rate, spam complaints, and inbox delivery rate (bounce rate).
It is especially important to build your workflow while keeping your desired outcomes in mind, such as the number of sales or leads the campaign should generate.
Analyze which audience segments respond best. For example, VIP customers may have a high open rate but few clicks, which could indicate that they are lacking personalization or relevant offers. Meanwhile, new subscribers usually have high open rates, but if conversions drop after a few emails, it may be worth reviewing the welcome series and adding extra incentives.
This can be facilitated through integration with Google Analytics (using UTM tags in links) or a CRM system, so you can track what a person did after clicking the email and what revenue it generated.
In addition to behavioral metrics, keep track of the technical aspects of delivery: ensure that the number of emails going to spam is not increasing, and check whether there’s an increase in bounces due to invalid email addresses.
Each email campaign is an opportunity to strengthen your relationship with customers. Mistakes in email campaigns can cost you customers, sales, and brand reputation. Poor subject lines, lack of segmentation, overloaded content, or technical issues often result in emails remaining unread or ending up in the spam folder.
However, if you account for all possible mistakes and segment your audience properly, your emails will be opened, read, and interacted with.
Head of Retention Marketing
I've been working in email marketing since 2016. I passed the way from a junior specialist with the thoughts "email is spam in the mailbox?" to the real jedi of retention marketing. I worked with the largest Ukrainian eCommerce projects. I'm keen of the latest technologies and non-standard technical implementations.
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