Summary
Marketing emails are blocked for various interconnected reasons encompassing sender reputation, list quality, authentication, content, and recipient-side factors. A low sender reputation due to spam complaints, blocklisting, or poor list hygiene negatively impacts deliverability. Failing to implement proper email authentication (SPF, DKIM, DMARC) or sending spoofed emails causes distrust from receiving servers. Spam filters are triggered by specific content elements and formatting. Recipient-side factors include IT policies and administrator actions that block emails at the corporate level. Proactive measures, such as list cleaning, reputation monitoring, email placement testing, and adhering to authentication best practices, are essential for ensuring successful inbox delivery.
Key findings
- Sender Reputation Impact: A low sender reputation resulting from spam complaints, blocklisting, or poor list hygiene negatively impacts deliverability.
- Authentication Importance: Lack of proper email authentication (SPF, DKIM, DMARC) or sending spoofed emails leads to distrust from receiving servers and potential blocking.
- Spam Filter Triggers: Spam filters are triggered by specific content elements, such as excessive capitalization, exclamation points, certain keywords, and poor formatting.
- Recipient-Side Factors: Recipient-side factors, including IT policies and administrator actions at the corporate level, can block emails.
- Email List Quality: The quality of your email list is crucial. Sending emails to outdated, invalid, or unengaged addresses can result in high bounce rates and spam complaints, leading to blocking.
- Microsoft 365 Filtering: Mail administrators can use Microsoft's advanced hunting feature to identify and understand why emails are blocked within Microsoft 365 environments.
- Migration Hard Bounces: During migration periods, IT providers may suppress emails if hard bounces from seed lists are detected.
- IP Reputation Matters: A poor IP address's reputation significantly impacts deliverability. Prior spam activity can lead to emails being blocked.
Key considerations
- Email Authentication: Implement and maintain SPF, DKIM, and DMARC to authenticate your emails and prevent spoofing.
- List Management: Regularly clean your email list by removing unengaged subscribers and validating email addresses to minimize bounce rates and spam complaints.
- Content Optimization: Optimize email content by avoiding spam trigger words, excessive capitalization, and exclamation points. Ensure clear and concise messaging.
- Reputation Monitoring: Monitor your sender reputation using available tools and services to identify and address potential issues promptly.
- Recipient Engagement: Focus on sending valuable and relevant content to engaged subscribers to improve open rates, click-through rates, and sender reputation.
- Whitelisting IPs: Provide specific IP addresses to recipients' IT teams for whitelisting, rather than requesting the whitelisting of entire ESPs, particularly when using shared IPs.
- Testing & Previewing: Test email deliverability and placement using tools like GlockApps to detect if emails land in the inbox, spam folder, or are blocked. Preview emails across different clients.
- IT Collaboration: When necessary, collaborate with recipient's IT to troubleshoot email delivery. Whitelisting may resolve a direct block.
What email marketers say
11 marketer opinions
Marketing emails are often blocked due to a combination of factors related to sender reputation, email list quality, authentication issues, content triggers, and technical configurations. Senders need to maintain a clean and engaged email list, ensure proper email authentication (SPF, DKIM, DMARC), avoid spam trigger words and formatting, monitor their sender reputation, and proactively test email placement to identify and resolve deliverability issues. Understanding and addressing these areas is crucial for ensuring marketing emails reach their intended recipients.
Key opinions
- Sender Reputation: A low sender reputation, often due to spam complaints or being listed on blocklists, is a primary reason for email blocking. Actively monitoring and managing your sender reputation is vital.
- Email List Quality: Poor list hygiene, including sending to invalid or unengaged addresses, leads to high bounce rates and spam complaints, negatively impacting deliverability.
- Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) makes it difficult for receiving servers to verify the legitimacy of your emails, leading to blocking or spam filtering.
- Content Triggers: Spam filters are often triggered by the use of all caps, excessive exclamation points, certain keywords, and poor formatting in email subject lines and content.
- Placement Testing: Testing email placement with tools can help identify whether emails are landing in the inbox, spam folder, or being blocked, providing insights into potential deliverability issues.
- Microsoft's Advanced Hunting Feature: Microsoft's advanced hunting feature can be used by mail administrators to locate and identify the reasons for emails being blocked at the mail filter level within Microsoft 365 environments.
- IT Provider Suppression: Emails may be suppressed due to actions taken by IT providers during events like migrations, especially if seed list emails are detected and hard bounce.
Key considerations
- List Hygiene: Regularly clean your email list by removing unengaged subscribers and validating email addresses to minimize bounce rates and spam complaints.
- Authentication Implementation: Implement SPF, DKIM, and DMARC to authenticate your emails and prevent spoofing. Ensure these records are properly configured.
- Content Optimization: Avoid using spam trigger words, excessive capitalization, and exclamation points in your email subject lines and content. Keep your messaging clear and concise.
- Sender Reputation Monitoring: Monitor your sender reputation using tools and services that provide insights into your sending metrics and identify potential issues.
- Engagement Tracking: Track email engagement metrics, such as open rates and click-through rates, to identify unengaged subscribers and optimize your content for better performance.
- Testing and Previewing: Test your emails across different email clients and devices to ensure they are displayed correctly and don't trigger spam filters. Previewing can help identify and fix formatting issues.
- Unsubscribe Accessibility: Make it easy for subscribers to unsubscribe from your emails to reduce the likelihood of spam complaints. Honour unsubscribe requests promptly.
Marketer view
Email marketer from Reddit explains that spam filters are often triggered by using all caps, excessive exclamation points, or certain keywords in your email subject lines and content. Keeping your messaging clear and concise can help avoid these triggers.
22 Sep 2022 - Reddit
Marketer view
Email marketer from GlockApps Blog shares that testing your email placement with tools like GlockApps helps you identify whether your emails are landing in the inbox, spam folder, or being blocked altogether, and provides insights into potential deliverability issues.
27 Mar 2022 - GlockApps Blog
What the experts say
6 expert opinions
Marketing emails are often blocked due to a combination of factors relating to the recipient's IT policies, IP address reputation, list quality, and authentication. Recipient-side blocking often involves IT teams implementing rules that prevent emails from reaching inboxes, potentially requiring whitelisting of specific IP addresses rather than entire ESPs. Sender-side issues, such as poor IP reputation stemming from previous spam activity and low-quality email lists, significantly impact deliverability. Authentication is also crucial; failing to implement SPF, DKIM, and DMARC can lead receiving servers to distrust messages, resulting in blocking or spam folder placement. A multi-faceted approach addressing both recipient-side and sender-side factors is necessary to improve deliverability.
Key opinions
- Recipient-Side Blocking: Emails can be blocked by recipient's IT teams due to internal policies and filtering rules. Whitelisting may be necessary.
- IP Reputation: A poor IP address reputation, often due to previous spam activity, can lead to email blocking.
- Email List Quality: Sending emails to outdated, invalid, or unengaged addresses can result in high bounce rates and spam complaints, leading to blocking.
- Authentication Failure: Failing to implement SPF, DKIM, and DMARC can cause receiving mail servers to distrust messages, resulting in blocking or spam folder placement.
- Corporate Troubleshooting: Troubleshooting email delivery within corporations involves examining the corporate's border security (e.g., Microsoft Cloud, Exchange) and working with the IT team to identify blocking rules or DMARC issues.
- Granular Whitelisting: Instead of whitelisting entire ESPs, it is better to whitelist specific IP addresses provided by the ESP, especially when using shared IPs.
Key considerations
- IT Collaboration: Engage with the recipient's IT team to identify and address blocking rules or authentication issues on their end.
- IP Reputation Management: Monitor and maintain a clean IP address by avoiding spam practices and promptly addressing any issues that arise.
- List Hygiene: Regularly clean your email list by removing invalid or unengaged addresses to minimize bounce rates and spam complaints.
- Email Authentication: Implement and properly configure SPF, DKIM, and DMARC to authenticate your emails and prevent spoofing.
- Troubleshooting Process: Systematically troubleshoot delivery issues by first verifying the ESP is sending emails, then investigating the corporate's border security and engaging with the recipient's IT team.
- Specific IP Whitelisting: Provide specific IP addresses to recipients for whitelisting, instead of requesting whitelisting of entire ESPs, particularly if using shared IPs.
Expert view
Expert from Word to the Wise (Laura Atkins) shares that failing to properly authenticate your emails using SPF, DKIM, and DMARC can cause receiving mail servers to distrust your messages, leading to blocking or spam folder placement. Proper authentication confirms you are who you say you are.
21 Jul 2022 - Word to the Wise
Expert view
Expert from Email Geeks explains the troubleshooting process for email delivery within a corporation, emphasizing the corporate's border (Microsoft Cloud or Exchange) as a key point of investigation after verifying the ESP is sending emails and suggests engaging the IT team to identify blocking rules or DMARC issues.
8 Aug 2021 - Email Geeks
What the documentation says
5 technical articles
Email blocking often occurs due to suspected spam, lack of email authentication (SPF, DKIM, DMARC), or poor domain/IP reputation. Major email providers like Gmail and Microsoft block emails identified as spam or spoofed, emphasizing the need for strong authentication protocols to verify senders. Consistent sending volumes, actively opted-in subscribers, and avoiding spam trigger words are also vital for avoiding spam filters. SPF, DKIM, and DMARC provide mechanisms for domain owners to authorize sending mail servers and define policies for handling authentication failures, thereby preventing spoofing and enhancing deliverability.
Key findings
- Spam Detection: Emails suspected of being spam are blocked by email providers.
- Authentication Importance: Lack of email authentication (SPF, DKIM, DMARC) is a primary reason for email blocking.
- Spoofing Prevention: Emails identified as spoofed, meaning they appear to come from your domain but are sent from an unauthorized source, are blocked.
- Reputation Impact: Poor domain or IP reputation contributes to email blocking.
- Authentication Standards: SPF, DKIM, and DMARC are crucial standards for authenticating email and preventing spoofing.
- DMARC Policy Enforcement: DMARC allows domain owners to define policies for handling emails that fail authentication checks, including quarantine or rejection.
Key considerations
- Implement SPF, DKIM, DMARC: Ensure proper implementation of SPF, DKIM, and DMARC to authenticate your email and prevent spoofing.
- Maintain Sending Volume: Establish a consistent sending volume to avoid triggering spam filters.
- Opt-In Subscribers: Ensure your subscribers have actively opted in to receive your emails.
- Avoid Spam Triggers: Avoid using spam trigger words and phrases in your email content.
- Monitor Reputation: Regularly monitor your domain and IP reputation to identify and address any issues that could impact deliverability.
- DMARC Policy: Carefully define your DMARC policy to balance security and deliverability. Start with a 'none' policy and gradually move to 'quarantine' or 'reject' as your authentication implementation matures.
Technical article
Documentation from Google Workspace Admin Help explains that Gmail might block emails if they're suspected of being spam, if the sending server isn't authenticated, or if the sending domain has a poor reputation. Resolving this can involve authenticating your email with SPF, DKIM, and DMARC.
24 Oct 2024 - Google Workspace Admin Help
Technical article
Documentation from DMARC.org explains that DMARC builds on SPF and DKIM to provide a policy for handling emails that fail authentication checks, allowing domain owners to specify whether to quarantine or reject such emails.
28 Dec 2023 - DMARC.org
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