Why are Zendesk Sell emails sent via Google API landing in Outlook/Hotmail spam despite passing SPF, DKIM, and DMARC?

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.

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.

Email marketer from Email Marketing Forum shares that tracking sender reputation with tools like Google Postmaster Tools and Microsoft SNDS is key. Low reputation can lead to spam filtering, despite authentication.

Email marketer from ActiveCampaign shares that poor email subject lines can lead to emails being marked as spam, and suggests always using subject lines that are clear, concise and not overly promotional.

Email marketer from EmailDrip Blog explains that a poor sender reputation, even with correct authentication, can result in emails landing in spam. They advise monitoring bounce rates, complaint rates, and engagement metrics to maintain a positive reputation.

Marketer from Email Geeks suggests to compare email headers from Zendesk Sell (the Google integration) with emails sent directly from gmail and check for comp auth failures.

Email marketer from Stackoverflow responds that the issue might be with recipients marking emails as spam. Even with authentication, high spam complaints can damage reputation. He suggests using feedback loops to monitor complaints and improve list management practices.

Email marketer from Mailjet shares that certain email content, such as spam trigger words, excessive use of images, or broken HTML, can cause emails to be flagged as spam even with proper authentication. They suggest using spam testing tools to analyze email content before sending.

Email marketer from MarketingPro shares that old or unengaged email addresses are likely spam traps and can damage the sender's reputation and decrease email deliverability rates. He/She suggests implementing a strategy to clean your email list to improve email deliverability rates.

Marketer from Email Geeks explains that the integration between Zendesk Sell and Google Workspace might be creating a pattern that is being matched against known spam. They suggest trying a dedicated outbound relay. As a 'cowboy fix', they propose putting an MTA in the middle to scrub the headers before passing on to Google, or relaying through SES to remove source headers.

Email marketer from Email Deliverability Blog responds that sudden spikes in email volume from new integrations like Zendesk Sell can trigger spam filters, even if authenticated. Ramp up volume slowly to establish trust with mailbox providers.

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.

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.

Expert from Word to the Wise explains that one potential cause for deliverability issues when sending via Google Workspace (even with proper authentication) is a poor reputation associated with Google's IP addresses, especially if the volume from a particular sender is low. This can cause filtering at Microsoft (Outlook/Hotmail) due to reputation or rate limiting issues. She suggests warming up the Google Workspace IP by sending consistent volume to legitimate recipients.

Expert from Spamresource shares that a common issue is an improper email configuration which can negatively affect deliverability even when SPF, DKIM, and DMARC is setup correctly. It suggests using mail flow logs to correctly configure your email settings and improve email deliverability rates.

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.

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.

Documentation from Google Postmaster Tools details Gmail's bulk sender guidelines, emphasizing the importance of consistent sending volumes, low spam complaint rates, and proper list hygiene. It recommends using authentication methods like SPF, DKIM, and DMARC, but also highlights the significance of sender reputation and engagement.

Documentation from RFC explains that while SPF, DKIM, and DMARC may pass for the main domain, DMARC policies for subdomains, especially if not explicitly set, can cause deliverability issues if the sending source (Zendesk Sell) is not properly authorized for that subdomain.

Documentation from Microsoft Support explains that Outlook/Hotmail uses various filtering mechanisms beyond SPF, DKIM, and DMARC, including user complaints, content analysis, and sender reputation. It advises monitoring your sender reputation using Microsoft's SNDS program.