Summary
Despite passing SPF, DKIM, and DMARC, Zendesk Sell emails sent via Google API may land in Outlook/Hotmail spam due to several technical and reputational factors. These include EC2 system configuration issues (EHLO, rDNS), Google Workspace IP reputation, general email configuration problems, complex filtering mechanisms beyond authentication, subdomain DMARC policies, improper bounce handling, incorrect return-path configuration, spam patterns created by the integration, content triggering spam filters, recipient spam complaints, volume spikes, and poor list hygiene. Addressing these requires a multi-faceted approach encompassing technical fixes, reputation management, and adherence to email best practices.
Key findings
- EC2 Configuration: Incorrect EC2 configuration (EHLO, rDNS) can trigger spam filters.
- IP Reputation (Google): Low sending volume and poor Google Workspace IP reputation can cause filtering.
- Email Misconfiguration: Incorrect email configuration can affect email deliverability even with proper authentication
- Advanced Filtering: Outlook/Hotmail uses filters beyond SPF, DKIM, DMARC, including user complaints and content analysis.
- Sender Reputation: Low sender reputation (spam complaints, low engagement) leads to spam filtering.
- Subdomain Policies: Incorrect subdomain DMARC policies cause deliverability issues.
- Bounce Handling: Improper bounce handling damages sender reputation.
- Integration Patterns: Zendesk Sell/Google Workspace integration creates spam patterns.
- Content Issues: Spam trigger words or broken HTML flag emails as spam.
- Volume Spikes: Sudden volume increases trigger spam filters.
- List Hygiene: Old/unengaged addresses act as spam traps.
- Return Path: Incorrect return path settings cause reduced deliverability rates
- Poor subject lines: If the subject lines of the emails sent are not clear, concise and overly promotional this can lead to email's landing in the spam folder.
Key considerations
- Fix EC2 Configuration: Correct EHLO and rDNS settings on the EC2 server.
- IP Warm-Up: Gradually increase sending volume to warm up the Google Workspace IP.
- Outbound Relay: Try a dedicated outbound relay or scrub headers with an MTA.
- Authentication Setup: Check authentication setup in Zendesk Sell.
- Monitor Reputation: Use Google Postmaster Tools and Microsoft SNDS.
- Feedback Loops: Use feedback loops to monitor and reduce spam complaints.
- List Management: Regularly clean your email list.
- Volume Ramp-Up: Gradually increase sending volume.
- Content Analysis: Analyze email content with spam testing tools.
- Subdomain DMARC: Configure DMARC policies for subdomains.
- Handle Bounces: Implement email bounce processing.
- Email Configuration: Use mail flow logs and check settings for email configuration
- Return path: Implement an email configuration check to ensure the return-path is setup correctly.
- Use high quality subject lines: Always use subject lines that are clear, concise and not overly promotional
What email marketers say
11 marketer opinions
Even when SPF, DKIM, and DMARC are correctly implemented, Zendesk Sell emails sent via Google API may still land in Outlook/Hotmail spam due to a variety of factors. These factors include the reputation of Zendesk Sell's shared IPs, content triggering spam filters, recipient spam complaints, sudden spikes in email volume, poor list hygiene (old/unengaged addresses), issues in the email setup (like improper return path) and poorly optimised subject lines. Monitoring sender reputation and implementing best practices in content, list management, and sending volume are crucial for improving deliverability.
Key opinions
- IP Reputation: Shared IPs used by Zendesk Sell can have a negative reputation due to other users' sending practices, leading to filtering even with proper authentication.
- Spam Patterns: The integration between Zendesk Sell and Google Workspace may create email patterns that are recognized as spam by Microsoft's filters.
- Content Issues: Specific email content, such as spam trigger words, excessive images, or broken HTML, can trigger spam filters despite authentication.
- Recipient Complaints: High spam complaint rates from recipients can significantly damage sender reputation and lead to spam filtering.
- Volume Spikes: Sudden increases in email volume, especially from new integrations, can trigger spam filters as a protective measure.
- List Quality: Old or unengaged email addresses can act as spam traps, harming sender reputation and deliverability.
- Poor email configuration: Improper email configuration, such as setting the return-path incorrectly, can negatively affect deliverability even with authentication.
- Poor subject lines: If the subject lines of the emails sent are not clear, concise and overly promotional this can lead to email's landing in the spam folder.
Key considerations
- Dedicated IP: Consider using a dedicated IP address for sending emails to maintain a good sender reputation.
- Content Analysis: Use spam testing tools to analyze email content and avoid spam triggers.
- Feedback Loops: Implement feedback loops to monitor spam complaints and address the underlying issues.
- List Management: Regularly clean your email list to remove old, unengaged, and potentially harmful addresses.
- Volume Ramp-Up: Gradually increase email volume to establish trust with mailbox providers and avoid triggering spam filters.
- Reputation Monitoring: Track sender reputation using tools like Google Postmaster Tools and Microsoft SNDS to identify and address any deliverability issues.
- Compare Headers: Compare email headers between Zendesk Sell sent messages vs a direct Gmail sent message to identify inconsistencies or potential issues.
- Check email configuration: Check mail flow logs to correctly configure your email settings.
- Check email configuration: Ensure the email subject lines that are used are clear, concise and not overly promotional.
Marketer view
Email marketer from Super User shares that shared IPs used by services like Zendesk Sell can have a negative impact on deliverability if other users are sending spam. He recommends using a dedicated IP address for sending emails to maintain a good sender reputation.
30 Jun 2021 - Super User
Marketer view
Email marketer from Reddit suggests that even with proper SPF, DKIM, and DMARC, third-party applications like Zendesk Sell can still cause deliverability issues due to their IP reputation or email formatting. He recommends checking if Zendesk Sell's IP is blacklisted and ensuring proper email authentication setup within Zendesk Sell.
21 May 2022 - Reddit
What the experts say
4 expert opinions
Even with proper email authentication (SPF, DKIM, DMARC), Zendesk Sell emails sent via Google API can end up in Outlook/Hotmail spam folders due to several expert-identified reasons. These include the EC2 configuration Zendesk uses (specifically the EHLO and rDNS), Google Workspace IP address reputation issues, and general email configuration problems. Addressing these underlying technical and reputation-based factors can improve deliverability.
Key opinions
- EC2 Configuration Issues: Zendesk's EC2 system configuration, particularly the 'localhost' EHLO and lack of custom rDNS, can trigger spam filters at Hotmail due to 2nd received line filtering.
- Google Workspace IP Reputation: A low sending volume combined with a potentially poor reputation of Google's IP addresses can cause Microsoft to filter emails.
- Improper Email Configuration: General email misconfiguration can affect email deliverability even when the key email authentication methods are implemented correctly.
Key considerations
- Fix EC2 Configuration: Consult with a competent vendor to correct the EHLO and rDNS settings on the EC2 server.
- IP Warm-Up: Gradually increase sending volume to legitimate recipients to warm up the Google Workspace IP address and improve its reputation.
- Review email configuration: Review email configuration by looking at mail flow logs and correct any errors to improve email deliverability rates.
Expert view
Expert from Email Geeks initially suggests that the DKIM signature might be the issue, recommending that it should be signed with the user's domain instead of Zendesk's/Amazon's. However, after reviewing the DKIM setup, they determine that it's configured correctly, ruling out an easy fix in that area. Also suggests the domain reputation could be an issue.
14 Oct 2021 - Email Geeks
Expert view
Expert from Email Geeks suggests the issue may stem from the configuration of the EC2 system Zendesk is using to connect to Google, specifically the EHLO being 'localhost' and the lack of custom rDNS. This configuration isn't resolved by relaying through Google and could be triggering 2nd received line filtering by Hotmail, which is causing the spam issue. They suggest finding a competent vendor to fix the EC2 server configuration.
24 Aug 2023 - Email Geeks
What the documentation says
5 technical articles
Even when SPF, DKIM, and DMARC are correctly implemented, emails sent via Google API can land in Outlook/Hotmail spam due to several reasons outlined in official documentation. These reasons include complex filtering mechanisms beyond authentication, subdomain DMARC policies, improper bounce handling, and return-path configuration. Maintaining good sender reputation, consistent sending practices, and proper technical configuration are crucial for deliverability.
Key findings
- Advanced Filtering: Outlook/Hotmail utilizes multiple filtering mechanisms besides SPF, DKIM, and DMARC, including user complaints, content analysis, and sender reputation.
- Sender Reputation: Google and Microsoft emphasize the significance of sender reputation, which is influenced by spam complaint rates, engagement metrics, and list hygiene.
- Subdomain Policies: DMARC policies for subdomains, if not explicitly set, can cause deliverability problems if the sending source is not properly authorized.
- Bounce Handling: Incorrectly handling email bounces can negatively affect your sender reputation and lead to reduced deliverability rates.
- Return-Path Configuration: Incorrectly configuring the return-path is critical when sending via a third-party tool such as Zendesk Sell and can negatively affect deliverability rates.
Key considerations
- Monitor Reputation: Monitor sender reputation using tools like Microsoft SNDS to identify and address deliverability issues.
- List Hygiene: Maintain proper list hygiene, which is the process of regularly cleaning email lists to remove unused or spam email addresses.
- Subdomain DMARC: Ensure DMARC policies are correctly configured for all subdomains used for sending emails.
- Handle Bounces: Implement email bounce processing to lower your sender reputation and increase email deliverability rates.
- Configure return-path: Make sure to correctly configure the return-path to ensure your email is set up correctly.
Technical article
Documentation from RFC shares how important it is to correctly configure the return-path in your email setup when using a third-party tool such as Zendesk Sell. If the return-path is incorrect this will negatively impact deliverability rates.
8 Mar 2024 - RFC Documentation
Technical article
Documentation from Hotmail Postmaster explains that how you handle email bounces matters to Microsoft's spam filtering algorithms. Failure to handle bounces properly can lower your sender reputation and decrease email deliverability rates.
9 Feb 2023 - Hotmail Postmaster
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