Email fails: The worst campaign mistakes and what to learn from them

At first glance, sending an email seems easy. Many people believe it’s as simple as opening an email platform, typing a message, and hitting send. But very few understand the craft behind a truly successful campaign.

Working at Scalero has taught me that email is an art. Sending an email correctly means understanding not just what message you want to share, but who you’re sharing it with. Once you know your audience, you need to communicate that information clearly to your Email Service Provider (ESP) so it knows exactly who should receive your message.

And before anything else, you must make sure you have permission from the user to send them emails. From there, every detail matters: the subject line, the preheader, the message itself, and your CTA (call to action). Each of these elements works together to determine whether your message connects or gets ignored.

Let’s break it down.

The elements of a successful email

• Subject line: The first impression. You have only seconds to catch your customer’s attention.

• Preheader: Once the subject grabs interest, the preheader reinforces your message and encourages the open.

• Body content: This is where you deliver value, clearly and concisely.

• CTA (Call to Action): Never send an email without one. If you don’t tell your reader what to do next, your message loses impact.

• Compliance: Always ensure your email follows legal requirements and includes a clear unsubscribe link.

Each of these steps seems simple, but mistakes can easily sneak in. And when they do, the results can range from mildly embarrassing to seriously damaging to your brand.

The most common email mistakes (and what to learn from them)

1. Poor deliverability and spam issues

If you don’t warm up your domain properly or send to uninterested users, providers might classify your messages as spam.
Lesson: Always warm up your domain, segment your audiences, and focus on engaged users. Quality over quantity to ensure a good deliverability. 

Example: Inbox placement collapse during ESP migration (Salesforce Marketing Cloud experts): Inbox placement fell to ~10% after a migration, then recovered to near 100% via re-warming and engagement-led suppression.

2.  Subject line and preheader errors

Misspellings, vague copy, or mismatched content between your subject and email can destroy credibility and lower open rates.
Lesson: Proofread every subject line, and make sure it aligns with your message. A/B test to learn what works best.

Example: Adidas (Boston Marathon, 2017): Subject line: “Congrats, you survived the Boston Marathon!” sparked backlash for insensitivity; Adidas issued a public apology. 

3. Design and rendering problems

Broken images or unresponsive layouts instantly hurt trust. Your email should look great across all devices and providers.
Lesson: Test your templates and preview across clients, especially Outlook, which often behaves differently. You can use platforms like Email on Acid to preview how your email renders across different providers and devices, ensuring a consistent experience for every recipient.

Example: Fab’s newsletter accidentally shipped with a random cat hero image, which was clearly off-brand and visible in screenshots of the live send.

4. Weak or broken CTAs

A missing or broken CTA link can ruin the entire campaign. Without a clear action, users simply close the email. An email without a correct CTA doesn’t do much.
Lesson: Always double-check link functionality and use actionable language (“Shop now,” “Get started,” “Book a demo”).

Example: Spotify: MailerLite documents a Spotify correction email sent after an earlier message contained an incorrect link; the follow-up clearly fixed the CTA destination.

Click-test every CTA; if a link ships wrong, send a fast correction.

5. Missing unsubscribe link

Leaving out an unsubscribe option isn’t just frustrating for the user, it can get your emails flagged as spam or rejected by your ESP.
Lesson: Always include a visible, working unsubscribe link. It builds trust and ensures compliance.

Example: Honda Motor Europe was fined £13,000 by the UK ICO for sending ~289,790 emails seeking consent without valid permission; regulators deemed them marketing messages.

6. Failing to test or QA before sending

A lack of QA is one of the biggest sources of preventable mistakes. From typos to broken personalization, these errors are easy to avoid. 
Lesson: Always run a comprehensive QA test before sending. Review content, links, renderings, and segmentation.

Example: We learned the hard way that if you set a date delay in the past in HubSpot, the platform skips users who are waiting for that date and moves them to the next step. 

This could have been avoided with more thorough QA.

What every email fail can teach you

Every brand, at some point, has made an email mistake. But the best ones learn from them. Each failure is an opportunity to improve processes, strengthen collaboration, and refine your strategy.

Email marketing is both a science and an art, and the more intentional you are with testing, design, and data, the better your results will be.

If you’re ready to take your email strategy to the next level, Scalero can help. We partner with brands to design, code, and automate lifecycle campaigns that convert.