What impact does malformed HTML have on email deliverability and spam filtering?
Summary
What email marketers say14Marketer opinions
Email marketer from Email Geeks suggests that content, including HTML, is becoming less relevant to spam filters than it was in the past, as filters now focus more on user preferences and engagement, ironically this means that content is more important to deliverability.
Email marketer from Email Geeks notes that common HTML errors in emails include missing alt text, unclosed tags, missing title tags, and missing `<!DOCTYPE html>`, and while fixing these takes minutes, the impact is marginal but can make a difference.
Email marketer from Email Geeks shares that common HTML errors include missing alt text, doctype, title, and unclosed tags, highlighting that missing alt text is particularly important due to accessibility concerns for users who don't automatically download images or who are visually impaired.
Email marketer from Stack Overflow explains that malformed HTML is one of the factors which can contribute to higher email spam scores; and recommends to validate the HTML of your email before sending, ensuring you're using the proper structure.
Email marketer from Email on Acid shares that HTML errors in emails can lead to inconsistent rendering across different email clients and devices. These inconsistencies can negatively affect user experience, leading to lower engagement rates and potentially increased spam complaints, harming deliverability.
Email marketer from Email Geeks shares that in the world of AI spam filters, misspelling a tag in HTML, if it's a common variable among spam, can negatively impact deliverability if other bad signals are also present.
Email marketer from EmailToolTester explains that your HTML email code can increase the chances of your emails being sent to the spam folder; and should be avoided.
Email marketer from Sendinblue responds that properly coding HTML emails ensures email clients can render your message properly; and can improve deliverability by avoiding triggers related to code quality.
Email marketer from Email Geeks shares that the impact of malformed HTML in emails depends on the sender's reputation; major mailbox providers are generally tolerant of it from previously good senders, though email clients like Outlook may react differently.
Email marketer from HubSpot explains that broken HTML can significantly impact your email deliverability, which can lead to higher bounce rates and lower engagement.
Email marketer from Neil Patel's Blog emphasizes that clean HTML is crucial for email deliverability, as malformed HTML can trigger spam filters. He recommends using a validator to ensure code is compliant and avoids common errors that negatively impact sender reputation.
Email marketer from Gmass explains that using valid HTML ensures the email will render correctly across all email service providers (ESPs), webmail clients and mobile devices, reducing issues which can lead to poor deliverability.
Email marketer from Reddit shares that Gmail's spam filters are sensitive to poorly formatted HTML. They recommend validating HTML, using proper DOCTYPE declarations, and avoiding excessive use of tables to maintain good deliverability to Gmail inboxes.
Email marketer from Email Geeks explains that spam scanning considers numerous variables with positive and negative values, such as DKIM signatures, malformed HTML, and spam complaints; malformed HTML can contribute negatively and affect deliverability.
What the experts say2Expert opinions
Expert from Word to the Wise (Laura Atkins) details that proper HTML structure and avoiding deprecated tags are important for deliverability, and not using these can lead to inconsistent display and can raise flags for spam filters.
Expert from Spam Resource explains that malformed HTML can negatively impact email deliverability as it can be a signal for spam filters. They advise ensuring clean and valid HTML code to improve inbox placement.
What the documentation says4Technical articles
Documentation from Apple details that malformed or invalid HTML can create accessibility issues for users on iOS devices; and that to ensure readability of your mail you should use valid HTML.
Documentation from Microsoft Support explains that malformed HTML in emails can cause Outlook to flag the message as junk. They suggest ensuring that HTML is properly formatted and complies with web standards to reduce the likelihood of emails being filtered into the junk folder.
Documentation from Litmus explains that poorly coded HTML emails are more likely to be flagged as spam. Using valid, semantic HTML ensures that email clients can properly render the message and improves deliverability by avoiding spam triggers related to code quality.
Documentation from Mailchimp specifies that emails with broken or non-standard HTML can trigger spam filters. They recommend following best practices for HTML email coding, including using inline CSS and avoiding deprecated HTML tags, to ensure optimal rendering and deliverability.