Does using bold text in emails affect deliverability?

Key findings

• Historical context: In the past, spam filters were more basic and often flagged emails with excessive or inconsistent HTML styling, including bold text, as suspicious. This was partly due to spammers often using complex or deceptive formatting to bypass early filters.
• Minimal direct impact: Modern spam filters are sophisticated and unlikely to flag an email solely because it contains bold text. They analyze a multitude of factors, with content relevance, sender reputation, and user engagement being far more critical than isolated formatting choices.
• Readability and engagement: Proper use of bold text can significantly improve email readability, helping recipients quickly grasp key information. Enhanced readability can lead to better engagement, which in turn positively impacts deliverability by signalling healthy sender behavior.
• Overuse and inconsistency: While isolated bolding is fine, excessive or inconsistent use of bold text (e.g., bolding entire paragraphs, frequent switching between styles, or having many empty bold tags) could still contribute to an overall spam score if it makes the email look like spam or low-quality content. Minimising the use of bold text, along with other elements like red font or excessive punctuation, is often advised by email platforms to ensure deliverability.

Key considerations

• Strategic use: Use bold text sparingly to highlight calls to action, key benefits, or critical information. The goal is to guide the reader's eye, not overwhelm it.
• Maintain consistency: Ensure your formatting is consistent throughout the email. Frequent and abrupt changes in font styles can appear unprofessional and potentially suspicious. (Source: Whitefluffy Cloud Support).
• A/B testing: If you are concerned about specific formatting, conduct A/B tests to observe the impact on your campaign's open rates, click-through rates, and deliverability metrics. Real-world data is always the most reliable indicator.
• Overall email health: Focus on broader email deliverability best practices, such as maintaining a clean list, sending relevant email content, and ensuring proper authentication, as these factors have a much larger impact than isolated formatting choices.

Key opinions

• No noticeable impact: Many marketers report they have never seen bolded text cause deliverability problems, considering it largely a non-factor in modern email environments.
• Historical irrelevance: Concerns about styling, like bold text, affecting deliverability are often dismissed as outdated, stemming from a time when spam filters were less sophisticated and spammers heavily relied on HTML tricks.
• Positive engagement potential: Some marketers have surprisingly found success with heavily bolded emails, indicating that for certain audiences, bolding can enhance readability and lead to better engagement.
• HTML cleanliness: As long as the HTML isn't riddled with excessive, empty, or malformed bold tags, basic bolding is unlikely to trigger spam filters. Clean email code quality is more important than specific styling elements.

Key considerations

• A/B testing is crucial: Marketers frequently recommend A/B testing email variations with different levels of bolding to observe actual impact on deliverability and engagement metrics for their specific audience (Source: Interseller).
• Audience demographics: The effectiveness and perception of bold text can vary with audience age or vision, suggesting that email template changes should consider recipient needs.
• Personalisation: Advanced marketers might consider personalising font weight and other styling based on user profiles to optimise readability and impact without affecting deliverability negatively.
• Avoid inconsistent styling: Frequent and erratic changes between bold, underlined, and normal text are viewed negatively by ISPs as they can indicate suspicious content, so consistency in styling is advised.

Key opinions

• Evolution of filters: Modern spam filters are highly sophisticated and are not typically triggered by simple formatting like bold text. Their algorithms are more advanced, focusing on behavioral patterns and overall context.
• Contextual analysis: The effectiveness of bold text is more about how it contributes to the overall readability and user experience of an email, rather than a direct deliverability factor.
• Indirect benefits: When bold text makes an email easier to read and understand, it can lead to higher engagement rates, which positively influences sender reputation and ultimately, deliverability.
• Over-optimization risk: Fixating on minor content elements like bolding can distract from more critical factors such as list hygiene, authentication (SPF, DKIM, DMARC), and overall content quality.

Key considerations

• HTML integrity: Ensure that the HTML structure is clean and well-formed. Bloated or excessively complex HTML (potentially from poor formatting practices) can sometimes raise flags for spam filters, irrespective of the bolding itself. This relates to email code analysis errors.
• Holistic deliverability view: Focus on the complete picture of your email sending practices. This includes strong authentication, positive engagement metrics, and avoiding known spam triggers, which outweigh isolated formatting concerns (Source: Vero Resources).
• Prioritize user experience: Design emails with readability in mind. If bold text enhances the user's ability to quickly scan and understand the message, its benefit likely outweighs any negligible deliverability risk.
• Continuous testing: Regularly test your email campaigns with various content and formatting elements to understand what resonates best with your audience and performs optimally across different inbox providers.

Key findings

• Readability as priority: Official documentation stresses that the primary purpose of any styling, including bold text, should be to improve the clarity and scannability of the email for the recipient.
• Avoid excess and inconsistency: Many guides caution against overusing bolding, writing in all caps, or frequently switching between different styling options, as this can be perceived as suspicious by ISPs (Internet Service Providers).
• HTML cleanliness: Documentation often implies that a well-structured, lightweight HTML email, free from unnecessary code or empty tags, is preferred by spam filters.
• Balance text and images: While not directly about bold text, many deliverability best practices highlight the importance of a good text-to-image ratio, suggesting that content richness is key.

Key considerations

• Spam indicator contribution: Although bold text itself is rarely a primary spam trigger, its misuse or excessive application can contribute to an overall spam score, especially when combined with other suspicious elements in the email's content (Source: Ontraport Support).
• Simplicity is valued: Documentation often suggests that emails that are lighter from a formatting perspective, with minimal stylistic flourishes and unnecessary HTML, are more likely to achieve better deliverability.
• Plain text version: Providing a clean and accurate plain text version of your HTML email is consistently recommended, as it improves accessibility and acts as a fallback for clients that don't render HTML well.
• Focus on content: Ultimately, the content itself—its value, relevance, and adherence to permission-based sending—holds more weight than minor formatting details like bolding when it comes to deliverability.