Why do emails sometimes end up in the spam folder?

Key findings

• Sender reputation: Your sending domain and IP address history heavily influence whether your emails reach the inbox or are flagged as spam. A poor reputation can lead to consistent deliverability issues.
• Authentication failures: Lack of proper authentication, like SPF, DKIM, and DMARC, makes your emails appear suspicious and prone to spam filtering.
• Content quality: The actual content of your email, including subject lines, images, and links, can trigger spam filters if it resembles typical spam patterns or uses certain keywords.
• Low engagement: If recipients rarely open, click, or reply to your emails, and frequently mark them as spam or move them to trash, it signals to mailbox providers that your content is not valued, leading to future spam placement.
• Blocklist inclusion: Being listed on an email blocklist (or blacklist) instantly flags your emails as spam by many providers. This often happens due to sending to spam traps or high complaint rates.

Key considerations

• Monitor deliverability: Regularly check your email deliverability and inbox placement using analytical tools.
• Implement authentication: Ensure your emails are properly authenticated with SPF, DKIM, and DMARC to build trust with mailbox providers.
• Maintain list hygiene: Regularly clean your email lists to remove inactive or invalid addresses, reducing bounces and spam trap hits.
• Focus on engagement: Send relevant content to segmented audiences to encourage opens and clicks, signaling positive engagement. For more details on why emails go to spam, Kinsta offers a comprehensive guide on reasons why your emails go to spam.

Key opinions

• Irony of spam: Marketers find it ironic when emails from deliverability companies or seemingly legitimate sources end up in spam, underscoring that no sender is immune.
• User influence: Average users marking emails as spam, even if inadvertently or out of habit, significantly contribute to an email's or sender's poor reputation.
• Provider neutrality: Even major providers like Microsoft or Google do not grant special privileges to their own internal emails, subjecting them to the same spam filtering rules.
• One mailbox doesn't mean everything: While a single instance of an email landing in spam is notable, marketers recognize that overall deliverability across many mailboxes is more indicative of a real issue.

Key considerations

• Content relevance: Marketers must focus on sending highly relevant and engaging content to reduce spam complaints and increase positive interactions.
• Avoid spam triggers: Vigilance is required to avoid keywords, poor formatting, or excessive links that might trigger spam filters, as detailed by OptinMonster on common spam reasons.
• Consent and expectations: Ensuring proper consent and setting clear expectations for email frequency and content can significantly reduce user-initiated spam reports.
• Regular audits: Performing regular checks on email content and sender reputation helps proactively identify and fix issues before they escalate.

Key opinions

• Reputation is paramount: Both IP and domain reputation are crucial. A poor sending history, even if from a previous user of your IP, can negatively impact your deliverability.
• Authentication is foundational: Properly configured SPF, DKIM, and DMARC records are essential for proving sender legitimacy and preventing spoofing, which directly influences spam filtering.
• Engagement signals: Positive engagement (opens, clicks, replies) and low negative engagement (spam complaints, deletions without opening) are key signals that inbox providers use to determine inbox placement.
• Blocklists matter: Inclusion on a public or private email blacklist (or blocklist) can severely impact deliverability, especially to major ISPs.

Key considerations

• Consistent sending: Maintaining a consistent sending volume and pattern helps build and stabilize your sender reputation with mailbox providers.
• Feedback loops: Utilize feedback loops provided by ISPs to quickly identify and remove users who mark your emails as spam, preventing further reputation damage.
• Segment your audience: Sending targeted content to segmented audiences improves engagement rates, which positively impacts your sender score.
• Proactive monitoring: Continuously monitor your domain and IP reputation, including checking against major blocklists and reviewing DMARC reports. Word to the Wise offers detailed insights on common email deliverability problems.

Key findings

• Mandatory authentication: Providers like Google and Yahoo now explicitly require strong authentication (SPF, DKIM, DMARC) for bulk senders.
• Easy unsubscribe: A clear, one-click unsubscribe mechanism is a fundamental requirement, significantly impacting user experience and reducing spam complaints.
• Spam complaint thresholds: Exceeding very low spam complaint rates (e.g., 0.1-0.3%) can immediately trigger stricter filtering or blocklisting.
• Reputation transparency: Tools like Google Postmaster Tools provide data on sender reputation and compliance.

Key considerations

• Technical compliance: Ensure your DNS records for SPF, DKIM, and DMARC are correctly configured and updated regularly to reflect changes in your sending infrastructure.
• List management: Implement strict list acquisition practices (e.g., double opt-in) and promptly remove invalid or unengaged addresses to maintain list quality.
• Content best practices: Adhere to content guidelines regarding image-to-text ratio, link quality, and avoidance of spammy phrasing, as outlined in documentation such as Mailchimp's guide on avoiding spam filters.
• Monitoring and adaptation: Continuously review postmaster tool data and adapt your sending strategy based on performance metrics and evolving ISP requirements.