Summary
Unexpected email sources in Mailgun logs, appearing to originate from a dedicated IP, can stem from several key factors. These include misconfigured Mailgun inbound routes that forward incoming email, misinterpretation of logs showing inbound traffic *to* the domain, and issues with email authentication (SPF, DKIM, DMARC) leading to spoofing concerns. Reputation problems with the IP or domain, blocklisting, and DNS configuration issues (missing or incorrect rDNS records) are also significant contributors. In rare cases, IP hijacking might be the cause. A sudden spike in sending volume from a new IP can also trigger spam filters. Actively monitoring logs, authentication configurations, reputation, and blocklists, along with proper warm-up procedures, are crucial for diagnosing and resolving the root cause.
Key findings
- Mailgun Inbound Routes: Misconfigured Mailgun inbound routes can forward incoming emails to your domain, making them appear as if they are originating from your dedicated IP.
- Log Misinterpretation: Logs may be showing inbound email *to* your domain, not outbound email from your IP.
- Authentication Issues: Missing or incorrect SPF, DKIM, and DMARC records can cause emails to be flagged as spoofed, harming deliverability.
- Reputation Problems: Issues with IP or domain reputation can lead to deliverability problems.
- Blocklisting: Being listed on public blocklists will significantly impact your email deliverability.
- DNS Configuration: Missing or misconfigured Reverse DNS (rDNS) records can cause delivery issues.
- IP Hijacking: In rare cases, a dedicated IP could be hijacked, leading to unauthorized sending.
- Sudden Sending Volume: A sudden surge in sending volume from a new IP can trigger spam filters.
Key considerations
- Review Mailgun Configuration: Carefully examine your Mailgun inbound routes to ensure they are correctly configured.
- Correctly Interpret Logs: Ensure you understand the Mailgun logs and distinguish between inbound and outbound traffic.
- Implement Authentication: Verify and correct SPF, DKIM, and DMARC settings for your domain.
- Monitor Reputation: Regularly monitor your IP and domain reputation using available tools.
- Check Blocklists: Check if your IP or domain is listed on public blocklists and take steps to delist if necessary.
- Correct DNS Settings: Ensure your Reverse DNS (rDNS) record is properly configured.
- Review Security: Review security measures to prevent IP hijacking.
- Warm-up IP: If using a new IP, gradually warm it up to build a positive sending reputation.
What email marketers say
10 marketer opinions
Unexpected email sources in Mailgun logs, appearing to originate from a dedicated IP, can stem from several reasons. These include misconfigured Mailgun inbound routes that forward incoming mail, the lack of proper email authentication (SPF, DKIM, DMARC) leading to spoofing concerns, and reputation issues related to either the dedicated IP itself or the sending domain. Blocklisting, missing or incorrect rDNS records, and the potential for shared IP impact (if not truly dedicated) further contribute. Establishing feedback loops and monitoring logs and blocklists are crucial for identifying and resolving the root cause.
Key opinions
- Mailgun Routes: Inbound Mailgun routes can forward emails to your domain, making them appear as if they originated from your dedicated IP.
- Authentication: Incorrect or missing SPF, DKIM, and DMARC records can cause emails to be flagged as spoofed, impacting deliverability.
- Reputation: ISPs consider both IP and domain reputation. A bad reputation on either can lead to delivery problems.
- Blocklists: Being listed on public blocklists will severely impact your email deliverability.
- rDNS Records: Missing or misconfigured Reverse DNS (rDNS) records can cause delivery issues, as it impacts sender verification.
- Shared IP Issues: If using a shared IP, the actions of other senders on the same IP can affect your deliverability.
Key considerations
- Review Mailgun Config: Check your Mailgun inbound routes to ensure they are configured correctly and not unintentionally forwarding unwanted emails.
- Implement Authentication: Ensure that SPF, DKIM, and DMARC are properly configured for your sending domain and IP address.
- Monitor Reputation: Regularly monitor your IP and domain reputation using tools and services provided by ISPs and reputation monitoring companies.
- Check Blocklists: Verify if your IP or domain is listed on any blocklists using tools like MXToolbox.
- Setup Feedback Loops: Establish feedback loops with major ISPs to receive reports on spam complaints and address issues proactively.
- Review Logs: Monitor Mailgun logs for bounces, complaints, and other delivery issues to identify and address problems quickly.
Marketer view
Email marketer from StackOverflow explains that you need to ensure that your SPF record includes your dedicated IP address. If not, other servers will think emails from that IP are spoofed. Check for typos and incorrect entries in your SPF record too.
19 Jan 2022 - StackOverflow
Marketer view
Email marketer from Mailgun Help Center explains that unexpected email sources showing in logs may be due to inbound routes configured in your Mailgun account. These routes can forward messages to your domain, making it appear as if the emails originated from your IP.
20 Jul 2024 - Mailgun Help Center
What the experts say
5 expert opinions
Unexpected email sources in Mailgun logs, appearing to originate from a dedicated IP, can be attributed to inbound mail being delivered *to* the domain rather than originating from it, misconfigured Reverse DNS (rDNS) records impacting sender verification, or even the rare possibility of IP hijacking. Additionally, incorrect or incomplete SPF records that don't authorize the dedicated IP can cause deliverability issues. Furthermore, a sudden surge in sending volume, especially from a new IP, can trigger spam filters.
Key opinions
- Inbound Traffic: The logs might be showing inbound email being delivered *to* your domain, which appears as originating from your IP.
- Misconfigured rDNS: A missing or improperly configured Reverse DNS (rDNS) record can lead to delivery problems due to failed sender verification.
- IP Hijacking: While uncommon, the dedicated IP could be hijacked or compromised, resulting in unauthorized email sending.
- Incorrect SPF: Incorrect or incomplete SPF records may not authorize your dedicated IP, causing emails to be flagged as suspicious.
- Sudden Sending Volume: A sudden spike in sending volume, especially from a new IP, can trigger spam filters and negatively impact your reputation.
Key considerations
- Verify Log Interpretation: Ensure you're correctly interpreting the Mailgun logs and distinguishing between inbound and outbound traffic.
- Check rDNS Configuration: Confirm that your Reverse DNS (rDNS) record is properly configured and matches your sending domain.
- Review Security: Assess your system's security measures and access logs to rule out the possibility of IP hijacking or unauthorized access.
- Correct SPF Records: Verify that your SPF record includes your dedicated IP and other authorized sending sources.
- Warm Up IP: If using a new dedicated IP, gradually warm it up by slowly increasing sending volume over time to establish a positive reputation.
Expert view
Expert from Spam Resource explains that a missing or misconfigured Reverse DNS (rDNS) record can be a primary reason for delivery issues, and thus might cause logs to show unexpected activity. Properly configuring rDNS to match your sending domain is essential for reputation and deliverability.
6 Apr 2024 - Spam Resource
Expert view
Expert from Word to the Wise explains that a sudden spike in sending volume, especially from a new IP, can trigger spam filters. Gradually warm up your dedicated IP to establish a positive sending reputation with ISPs.
20 Feb 2022 - Word to the Wise
What the documentation says
4 technical articles
Unexpected email sources in Mailgun logs can stem from a lack of proper DNS configuration (missing or incorrect A and PTR records), inadequate email authentication (SPF, DKIM) leading to potential spoofing, and the absence of a DMARC policy to instruct receivers on how to handle unauthenticated emails. Reviewing Mailgun logs to understand bounce, drop, and complaint events is crucial for diagnosing delivery issues.
Key findings
- DNS Configuration: All internet-reachable hosts must have both forward (A record) and reverse (PTR record) DNS entries. Failure to do so can lead to mail delivery issues.
- DMARC Policy: A DMARC policy allows senders to indicate that their emails are protected by SPF and/or DKIM, and tells receivers how to handle emails that fail authentication.
- Mailgun Log Analysis: Reviewing Mailgun logs for bounces, drops, and complaints helps diagnose the root causes of delivery problems.
- DKIM Authentication: DKIM is an email authentication system designed to detect email spoofing by verifying that an email message claimed to have come from a specific domain was authorized by the owner of that domain.
Key considerations
- Implement Proper DNS: Ensure your domain has properly configured A and PTR records.
- Establish DMARC Policy: Implement a DMARC policy to instruct receiving mail servers on how to handle unauthenticated emails from your domain.
- Analyze Mailgun Logs: Regularly review Mailgun logs to identify and address delivery problems, such as bounces and complaints.
- Implement DKIM Signing: Ensure that all outgoing emails are properly DKIM-signed to authenticate the origin of the message.
Technical article
Documentation from RFC Editor explains that it is important to ensure that all Internet-reachable hosts have both forward (A record) and reverse (PTR record) DNS entries. Failure to do so can lead to mail delivery issues.
23 Oct 2023 - RFC Editor
Technical article
Documentation from DMARC.org explains that a DMARC policy allows a sender to indicate that their emails are protected by SPF and/or DKIM, and tells a receiver what to do if neither of those authentication methods passes – such as quarantine or reject the message.
12 Oct 2021 - DMARC.org
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