Summary
Emails delivered internally but not externally often face a combination of challenges related to sender reputation, authentication, content filtering, network configurations, and recipient-specific settings. Internal networks commonly bypass standard security and reputation checks, while external servers enforce stricter policies. Key issues include: poor IP/domain reputation, incorrect SPF/DKIM/DMARC authentication, aggressive spam filtering based on content or code patterns, local or misused image URLs, internal whitelisting bypassing external checks, incorrect email routing rules, and deliverability impacted by email client variances. It's also vital to verify recipient spam folders and check if their domains are protected by services like ProofPoint. Best practices include following ESP workflows, testing with external email addresses, engaging with IT support, and improving engagement metrics by maintaining clean and engaged email lists.
Key findings
- Reputation & Authentication: External servers place higher importance on the sender's IP/domain reputation and proper SPF, DKIM, and DMARC authentication compared to internal systems.
- Filtering & Content: External spam filters are stricter, scanning email content and code for spam triggers or formatting errors, where internal networks often have more lenient filters.
- Network Configuration: Internal networks may bypass standard DNS checks or apply different routing rules than external mail servers, impacting external delivery.
- Internal Whitelisting: Many organizations whitelist their own domain internally, leading to successful internal delivery while external recipients face standard deliverability hurdles.
- Domain Protections: Recipient domains may utilize email security services (e.g. ProofPoint) that quarantine messages before they reach user inboxes.
- Engagement: Poor email engagement metrics (low opens, clicks) can negatively impact deliverability to external recipients.
Key considerations
- Verify Basic Delivery: Ensure that recipients have checked their spam folders and searched by subject line before pursuing more complex investigations.
- Check Image URLs: Confirm that all image URLs are publicly accessible and not linked to internal resources.
- Follow ESP Workflow: Adhere to the guidelines and procedures provided by your email service provider for creating and sending campaigns.
- Test Externally: Always send test emails to external email accounts (Gmail, Yahoo, etc.) to identify deliverability issues.
- Examine 'Show Original': Analyze the 'Show Original' email header for insights into deliverability problems.
- Contact IT Support: Involve the recipient's IT team to investigate potential domain-level filtering or quarantine issues.
- Review DNS Records: Confirm that SPF, DKIM, and DMARC records are correctly configured to authenticate your domain.
- Maintain List Hygiene: Practice double opt-in and regularly clean your email list to remove unengaged subscribers.
- Consider Dedicated IP: Use a dedicated IP address for sending emails to manage and build a positive sender reputation.
What email marketers say
16 marketer opinions
Emails may be delivered internally but not externally due to various factors related to reputation, authentication, filtering, and network configurations. Internal networks often have whitelisting or less stringent security measures than external networks. External servers are more likely to check for proper authentication (SPF, DKIM, DMARC), scrutinize sender reputation (IP and domain), employ stricter spam filters, and enforce email content standards. Quarantine folders and IT-managed filtering systems can also block external emails. Dedicated IPs, list hygiene, engagement metrics, and email rendering differences can affect deliverability.
Key opinions
- Reputation Matters: IP and domain reputation influence external deliverability; internal networks often bypass reputation checks.
- Authentication is Key: External servers rigorously check SPF, DKIM, and DMARC records; internal servers may not.
- Filtering Differences: External spam filters are more aggressive and might block emails based on content, while internal filters are more lenient.
- Internal Whitelisting: Companies often whitelist their own domains internally, bypassing external deliverability hurdles.
- Quarantine Effects: Emails can be caught in quarantine folders, especially on domains managed by providers like ProofPoint.
- Engagement Impact: Low engagement (opens, clicks) negatively affects email placement with external providers.
Key considerations
- Check IP/Domain Reputation: Assess the reputation of your IP address and domain using online tools to identify potential blacklisting issues.
- Verify Authentication Settings: Ensure SPF, DKIM, and DMARC records are correctly configured to authenticate your emails.
- Test with External Accounts: Send test emails to external email addresses (Gmail, Yahoo) to identify deliverability problems.
- Review Email Content: Examine email content for spam triggers or coding errors that external filters might flag.
- Monitor Engagement: Track engagement metrics and clean your email list to remove unengaged recipients.
- Investigate Quarantine: If possible, check with recipients if the email has been directed to a quarantine folder by their mail provider.
- Use Dedicated IP: Consider using a dedicated IP address to manage your sending reputation, especially if you send high email volumes.
Marketer view
Email marketer from Reddit explains that your domain's reputation is crucial for external deliverability. If your domain has a history of spam complaints, external servers are more likely to block your emails. Internal servers often have better trust for internal domains.
20 Dec 2023 - Reddit
Marketer view
Marketer from Email Geeks explains that if emails were initially accepted but didn't reach inboxes, a spam filter might have removed them, or they might be in an IT-managed quarantine.
8 Oct 2024 - Email Geeks
What the experts say
8 expert opinions
Emails delivered internally but not externally often face deliverability challenges due to bypassed DNS checks, varying sender reputation, and differing network configurations. Initial troubleshooting involves verifying spam folders and subject line searches. Technical issues like local image URLs can cause problems. It's crucial to follow ESP workflows and test with external email addresses. Internal networks bypass DNS/SPF/DKIM checks external servers use and internal setups whitelist internal emails, masking issues. Sharing 'Show Original' details and seeking IT assistance can help identify problems.
Key opinions
- Initial Checks Important: Verifying spam folders and subject line searches can rule out simple delivery issues.
- Local Resources Cause Issues: Linking to local image URLs or internal file servers can cause external servers to reject emails.
- ESP Workflow is Key: Following the email service provider's recommended workflow helps catch and fix deliverability issues.
- Testing with External Addresses Reveals Issues: Testing with external email addresses, like Gmail, helps expose delivery problems hidden by internal whitelisting.
- DNS Checks Bypassed Internally: Internal networks often bypass DNS/SPF/DKIM checks, which external servers enforce.
- Sender Reputation Varies: Sender reputation differs across ISPs; internal networks may have pre-existing positive reputation.
Key considerations
- Recipient Investigation: Initially confirm recipients have checked spam folders and searched for the email.
- Review URL Structure: Ensure that image URLs are publicly accessible and not pointing to local resources.
- Check ESP settings: Fix any errors picked up by the ESP after running the email campaign through Litmus.
- External Testing is Essential: Always test email campaigns with external addresses before sending them to a broader audience.
- Share 'Show Original': If issues persist, share the 'Show Original' data with experts for further analysis.
- Involve IT Team: If deliverability remains an issue, recipients should engage their IT team for deeper investigation.
- Correct DNS settings: Ensure SPF and DKIM settings are correct.
Expert view
Expert from Email Geeks advises to first verify if recipients checked their spam folders and searched by subject line. He mentions that content-based issues rarely cause emails to completely vanish, so this initial check is crucial.
19 Dec 2021 - Email Geeks
Expert view
Expert from Email Geeks suggests having a recipient ask their IT team to investigate the issue, as they have the necessary information and a paid account with ProofPoint for assistance.
9 Nov 2023 - Email Geeks
What the documentation says
4 technical articles
Emails delivered internally but not externally are often affected by routing rules, filtering policies, content formatting, and reputation systems. Google Workspace's custom routing and Microsoft's Exchange Online Protection (EOP) apply different rules internally versus externally. Strict formatting of Content-Type headers and MIME types, as defined in RFC 7231, is essential for external delivery. Cisco's SenderBase Reputation system influences deliverability based on spam volume and blacklisting.
Key findings
- Routing Rules Matter: Custom email routing rules in Google Workspace can affect internal vs. external delivery.
- Filtering Policies Differ: Microsoft EOP applies different filtering policies to internal and external emails.
- Content Formatting Is Key: Correct Content-Type headers and MIME types, as per RFC 7231, are crucial for external acceptance.
- Reputation Systems Impact Delivery: Cisco's SenderBase Reputation system can block or filter emails based on IP/domain reputation.
Key considerations
- Review Routing Settings: Check Google Workspace routing rules to ensure external emails are correctly routed.
- Assess EOP Filtering: Examine Microsoft EOP filtering policies for potential external email blocks.
- Validate Content Formatting: Ensure HTML emails adhere to RFC 7231 standards for Content-Type and MIME types.
- Monitor SenderBase Reputation: Check your IP/domain reputation on Cisco's SenderBase to identify potential issues.
Technical article
Documentation from Google Workspace Admin Help explains that Google Workspace allows administrators to set up custom email routing rules. These rules can affect how emails are delivered internally versus externally. Incorrect routing settings might cause external emails to be blocked or filtered.
8 May 2024 - Google Workspace Admin Help
Technical article
Documentation from RFC 7231 explains that the Content-Type header and MIME types in HTML emails must be correctly formatted. External servers might be stricter about enforcing these standards, and if there are errors, emails may be rejected or filtered.
3 Jul 2021 - RFC 7231
Are SPF, DKIM, and DMARC records necessary for transactional email servers not used for marketing?
Do SPF and DKIM records need to be aligned for all email service providers?
How can I ensure email compliance with Yahoo/Google rules including DMARC, SPF, and FcrDNS?
How do SPF, DKIM, and DMARC affect email deliverability with Cvent?
How do SPF, DKIM, and DMARC email authentication standards work?
What are SPF, DKIM, and DMARC, and when are they needed?
