Are spam trigger words still a major concern for email deliverability?

No, traditional spam trigger word lists are largely outdated for modern email filters. These filters (or blocklists) now prioritize factors like sender reputation, engagement metrics, and authentication protocols over specific keywords. While extremely egregious or deceptive language can still be flagged, a few isolated "spammy" words typically won't impact a reputable sender.

Do PDF attachments negatively affect email deliverability?

Yes, directly attaching PDFs or other files to emails can significantly hurt your deliverability. Attachments are often flagged by spam filters due to security concerns, as they are a common vector for malware. It's best practice to host your document online and include a link to it in your email instead.

Are links in emails bad for deliverability or email warm-up?

Links are generally not bad for deliverability, provided they are relevant, minimal in quantity, and point to reputable domains (ideally your own). However, using too many links, suspicious links, or link shorteners can raise red flags with spam filters. Focus on quality and transparency when including links.

What are the best practices for email warm-up concerning content?

During email warm-up, it's crucial to build a positive sender reputation. Focus on sending highly relevant and engaging content to active subscribers. Avoid sending emails with direct attachments or an excessive number of links. Prioritize consistent sending volume and monitor your engagement metrics closely.

Are spam trigger words, PDF attachments, and links bad for email warm-up and deliverability? - Sender reputation - Email deliverability - Knowledge base

When starting a new email campaign or warming up a new domain, questions often arise about what content elements might hinder deliverability. Many marketers still wonder if certain words, attachments, or links could trigger spam filters or negatively impact their sender reputation. It is a common misconception that strict adherence to outdated lists of "spam words" is paramount, or that any attachment will immediately land an email in the junk folder.

The landscape of email deliverability is constantly evolving, with modern spam filters becoming increasingly sophisticated. They prioritize sender reputation, engagement, and authentication protocols (like DMARC, SPF, and DKIM) over simple content-based triggers. This article will explore the real impact of spam trigger words, PDF attachments, and links on your email warm-up process and overall deliverability, offering best practices to ensure your messages reach the inbox.

Spam trigger words: an outdated concern?

For years, email marketers meticulously avoided specific "spam trigger words" like "free," "guarantee," or "urgent," fearing their emails would be immediately flagged. While such lists were once highly relevant, the effectiveness of keyword filtering has significantly diminished over time. Modern spam filters are far more advanced than simple word-matching algorithms, focusing instead on a holistic view of email characteristics and sender behavior.

Today, a sender's reputation is the primary determinant of inbox placement. If your domain and IP address have a good sending history, high engagement rates, and low complaint rates, the presence of a few traditionally "spammy" words will likely have minimal impact. Conversely, if your sender reputation is poor, even the most innocuous email content might land in the spam folder. Understanding this shift is crucial for effective email strategy, especially during a new domain warm-up phase. You can read more about the declining relevance of specific spam trigger words at Spam Resource.

There are, however, rare and unpredictable exceptions where certain words might temporarily trigger a spam filter (or blocklist) for a specific email provider, even if that word isn't typically considered "spammy." These instances are usually short-lived and reflect a dynamic, constantly updated filtering system, not a static list. Focusing too much on avoiding these phantom words can distract from more impactful deliverability strategies, such as maintaining a clean list and securing your email authentication. For more information, explore whether spam trigger words are still relevant for deliverability.

Focus on reputation, not just keywords

While keyword lists can provide a basic understanding of what to avoid, modern email deliverability hinges on a sender's overall reputation. This encompasses factors like sender domain age, IP reputation, email authentication (SPF, DKIM, DMARC), bounce rates, spam complaint rates, and user engagement. A strong reputation allows for more flexibility in content, whereas a poor one will cause issues regardless of the words used.

During email warm-up, focus on sending highly relevant content to engaged recipients to build a positive sender reputation. Don't obsess over individual words, but rather on providing value and avoiding anything that might lead to a spam complaint. Learn more about what spam trigger words are and their impact.

PDF attachments: a significant deliverability hurdle

Attaching PDF files directly to emails is generally a bad idea for deliverability, especially during email warm-up or when contacting leads who have only recently opted in. While it might seem like a straightforward way to share documents, attachments introduce significant risks that can trigger spam filters and even lead to your emails being silently discarded without a bounce notification. This is particularly true for new senders or those trying to establish a positive reputation.

Email attachments, particularly PDFs, are frequently exploited as a vector for malware and phishing attacks. Corporate email filters and inbox providers (like

Gmail and

Outlook) are highly suspicious of emails with attachments from unverified or new senders. This caution is a necessary security measure, but it means legitimate emails with PDFs can suffer. It's not just about the content of the PDF, but the very act of attaching a file that raises a red flag. Learn more about how PDF attachments negatively impact deliverability.

Instead of attaching a PDF, the recommended best practice is to host your document online (e.g., on your website, Google Drive, Dropbox) and provide a link to it within your email. This approach offers several benefits: it reduces the email's size, bypasses attachment-based spam filtering, and allows you to track clicks on the link, providing valuable engagement data. Even linking to a PDF on a file-sharing service can be better than a direct attachment, though linking directly to your own domain is preferred. As Campaign Refinery highlights, attachments can significantly damage email deliverability. Consider alternative approaches to sending PDFs via email.

Direct PDF attachment

Risk of blocking: High likelihood of being flagged or silently discarded by corporate and public spam filters, especially from new or low-reputation senders.
Malware concerns: Widely used for distributing malicious software, making all attachments inherently suspicious to security systems.
Email size: Can significantly increase email size, leading to slower delivery or hitting recipient mailbox limits.
Tracking: No direct way to track if the recipient opened or viewed the attached document.

Links and email deliverability: quality over quantity

The impact of links on email deliverability is nuanced. Generally, including links to your website or other reputable sources is not inherently bad for deliverability. In fact, for legitimate senders, links can be a positive signal, indicating that the email content is driving engagement and directing recipients to valuable resources. The key lies in the quality and quantity of these links, as well as the reputation of the domains they point to. For insights on this, refer to discussions about whether linking to PDFs is bad for deliverability.

Problems arise when links are used deceptively or excessively. For instance, using too many links, especially in the early stages of email warm-up, can appear suspicious to spam filters. Link shorteners (like Bitly or TinyURL) are also often viewed with suspicion because they can mask malicious destinations, making them a common tactic for spammers. It's almost always better to use full, descriptive links that clearly indicate their destination.

The reputation of the linked domain is also critical. If you link to domains known for spam or phishing, it will undoubtedly hurt your own sender reputation. Stick to linking to your own well-maintained website or other highly reputable sources. During warm-up, focus on including a minimal number of relevant links to your primary domain to establish positive associations. This helps build trust with inbox providers. Check out more details on HTTP links and spam filters.

Link type	Impact on deliverability
Links to your main domain	Generally positive, especially if your domain has a good reputation. These indicate legitimate activity.
Links to reputable third-party sites	Neutral to positive. Linking to well-known, trusted sources (e.g., news sites, academic papers) is usually fine.
Link shorteners	Often viewed with suspicion due to their use in phishing. Avoid during warm-up and for critical emails. Adding links to cold emails can negatively affect deliverability.
Excessive links	Too many links, especially in the body of the email, can appear spammy. Keep it concise and relevant.

Views from the trenches

Best practices

Always prioritize building and maintaining a strong sender reputation through consistent, high-quality sending practices.

Instead of direct attachments, host your files on your website or cloud storage and provide a clear, descriptive link.

Use full, legitimate links to your own domain or highly reputable third-party sites, avoiding generic link shorteners.

Monitor your email deliverability metrics closely, including open rates, click-through rates, and complaint rates.

Segment your audience and send relevant content to engaged users to foster positive interactions.

Implement and correctly configure SPF, DKIM, and DMARC for robust email authentication.

Common pitfalls

Over-focusing on avoiding "spam words" while neglecting fundamental sender reputation factors.

Attaching PDFs or other files directly to emails, especially when sending to a cold or unengaged audience.

Using multiple or suspicious-looking links, including masked URLs or those pointing to low-reputation domains.

Sending emails to unverified or old email lists, which can lead to spam traps and high bounce rates.

Failing to regularly clean your email list of inactive subscribers and invalid addresses.

Ignoring email authentication protocols, leaving your domain vulnerable to spoofing and phishing.

Expert tips

Spam filtering systems have evolved beyond simple keyword matching, focusing on sender behavior and reputation.

Even with a good reputation, a sudden change in email volume or content can temporarily trigger filters.

The content of your email (e.g., plain text vs. HTML, image-to-text ratio) also plays a role in deliverability.

Regularly check your domain and IP on major blocklists to ensure you haven't been inadvertently listed.

Personalization and segmentation can significantly improve engagement, a key factor for good deliverability.

A gradual increase in sending volume (warm-up) is essential for new domains to build trust with ESPs.

Expert view

Expert from Email Geeks says spam words are an outdated concern, with only a few minor and unusual exceptions.

2024-02-26 - Email Geeks

Marketer view

Marketer from Email Geeks says that if links to your site are associated with wanted email, then their inclusion is neutral to slightly positive for deliverability.

2024-02-26 - Email Geeks

Modern email deliverability: focus on reputation and engagement

In the contemporary email landscape, the focus for achieving high deliverability, particularly during email warm-up, has shifted dramatically. Obsessing over "spam trigger words" or avoiding all links is largely an outdated strategy. Instead, success hinges on establishing and maintaining a strong sender reputation, ensuring proper email authentication, and sending valuable content to an engaged audience.

Direct PDF attachments pose significant risks and should be avoided in favor of linking to hosted documents. Links, when used appropriately and pointing to reputable domains, are not detrimental and can even be beneficial. By prioritizing these core principles, you can navigate the complexities of email deliverability and ensure your messages consistently land in the inbox, fostering better communication and campaign performance.