Summary
Sailthru emails might send via shared IPs despite having dedicated IPs for several reasons. SparkPost may misreport IPs, showing internal filtering IPs instead of dedicated ones. Other factors include IP warm-up processes using shared IPs, specific routing configurations for transactional or less engaged users, and volume thresholds in Sailthru that automatically route lower volume emails via shared IPs. DNS misconfigurations (SPF/DKIM) can also cause this issue. Shared IPs might protect dedicated IP reputation. Multi-tenancy and reporting or configuration errors can cause the wrong sending IP to be used. Testing tools might misattribute IPs as well.
Key findings
- Reporting Errors: SparkPost might report internal filtering IPs instead of dedicated IPs, misrepresenting the sending source.
- IP Warm-up: Shared IPs are used during IP warm-up phases to ensure deliverability while dedicated IPs are being established.
- Strategic Routing: Sailthru might be configured to route specific email types (e.g., transactional or low engagement) through shared IPs based on volume, reputation, or deliverability strategies.
- Volume Thresholds: Lower email volume may be automatically routed through shared IPs due to volume thresholds configured within Sailthru.
- DNS Configuration: DNS misconfigurations, especially in SPF and DKIM records, can lead to emails being routed through shared IPs instead of dedicated IPs.
- Reputation Protection: Shared IPs may be used to protect the reputation of dedicated IPs, especially when the dedicated IPs face deliverability challenges.
- Configuration or Coding Errors: Configuration or coding errors with a 3rd party ESP can cause the wrong sending IP to be used.
- Multi-Tenancy: The multi-tenant nature of shared platforms can result in unexpected routing through shared IPs due to system architecture.
- Testing Tool Inaccuracies: Email testing tools might misattribute sending IPs, leading to false reporting of shared IPs.
Key considerations
- Verify Reporting Accuracy: Confirm IP reporting accuracy with SparkPost and investigate any discrepancies to ensure correct data.
- Review Sailthru Configuration: Carefully review Sailthru's routing rules, volume thresholds, and fallback settings to understand email traffic management.
- Audit DNS Records: Thoroughly audit SPF and DKIM records for proper configuration to prevent misrouting and ensure dedicated IPs are correctly associated with sending domains.
- Monitor IP Reputation: Actively monitor the reputation of both dedicated and shared IPs to identify and mitigate potential deliverability issues proactively.
- IP Warm-up Management: Monitor IP warm-up progress and ensure that dedicated IPs are correctly and efficiently ramped up to reduce reliance on shared IPs.
- ESP Configuration Audit: Periodically audit your ESP configuration to look for configuration errors that would cause dedicated IPs to not be used.
What email marketers say
10 marketer opinions
Sailthru emails might be sending through shared IPs despite dedicated IPs due to several reasons. SparkPost's reporting could be inaccurate, showing internal filtering IPs instead of actual sending IPs. Other potential causes include IP warmup processes, routing configurations for transactional or less engaged users, volume thresholds in Sailthru, and misconfigurations in DNS settings (SPF/DKIM). Multi-tenancy on shared platforms can also lead to unexpected routing. Email testing tools might also misattribute IPs.
Key opinions
- Reporting Inaccuracy: SparkPost's platform might misreport IPs, showing internal filtering IPs instead of the dedicated IPs.
- IP Warmup: Shared IPs might be used during the IP warmup process or for overflow volume.
- Routing Configuration: Sailthru might be configured to route certain email types (transactional, low-engagement) through shared IPs.
- Volume Thresholds: Lower volume emails might be automatically routed through shared IPs.
- DNS Misconfiguration: Misconfigured DNS settings, particularly SPF and DKIM records, can cause emails to be sent through shared IPs.
- Multi-Tenancy: The multi-tenant architecture of the platform can sometimes lead to unexpected IP routing.
- Testing Tool Misattribution: Email testing tools may incorrectly attribute sending IPs.
Key considerations
- Verify Reporting: Confirm the accuracy of IP reporting with SparkPost support.
- Check Sailthru Configuration: Review Sailthru's routing rules, volume thresholds, and fallback settings.
- Audit DNS Records: Ensure SPF and DKIM records are correctly configured for your dedicated IPs.
- Monitor IP Reputation: Monitor the reputation of both dedicated and shared IPs to identify any deliverability issues.
- Testing Processes: Ensure you are testing your emails correctly and checking they are being sent from the correct IP.
Marketer view
Marketer from Email Geeks asks if Karoline is doing an IP warm up and using the automated process that directs overflow volume to the shared IP pool.
9 Nov 2022 - Email Geeks
Marketer view
Email marketer from Email On Acid suggests it could be due to a routing issue where Sailthru is configured to send certain types of emails (e.g., transactional emails or emails to less engaged users) through shared IPs to protect the reputation of dedicated IPs.
11 Nov 2022 - Email On Acid
What the experts say
2 expert opinions
Email platforms like Sailthru might use shared IPs alongside dedicated IPs for various reasons. This can include routing specific email types (transactional/automated) based on volume, reputation, or deliverability strategies. Additionally, configuration or coding errors within the ESP could cause emails to be sent from shared IP pools if not properly associated with dedicated IPs.
Key opinions
- Strategic IP Usage: Shared IPs may be intentionally used for certain types of emails based on volume, reputation, or deliverability strategies.
- Configuration Errors: Coding or configuration errors can cause emails to be misrouted and sent from shared IP pools instead of dedicated IPs.
Key considerations
- Review Email Routing: Examine email routing configurations to understand which email types are being sent via shared IPs and why.
- Audit ESP Configuration: Check configuration within the ESP to look for configuration errors that would cause dedicated IPs to not be used.
- Monitor Deliverability: Continuously monitor deliverability rates on both dedicated and shared IPs to identify any potential issues.
Expert view
Expert from Spam Resource explains that configuration or coding errors with a 3rd party ESP can cause the wrong sending IP to be used. If the message isn't properly associated with the dedicated sending IP, it may be accidentally sent from a shared IP pool.
22 Oct 2023 - Spam Resource
Expert view
Expert from Word to the Wise, Laura Atkins, shares that sometimes email platforms utilize shared IPs for specific types of emails (like transactional or automated messages) even when dedicated IPs are present, based on volume, reputation, or deliverability strategies.
22 Nov 2021 - Word to the Wise
What the documentation says
5 technical articles
Email platforms like Sailthru might utilize shared IPs despite the presence of dedicated IPs for several documented reasons. These include using shared IPs during IP warm-up to maintain deliverability, potential IP reporting discrepancies that show internal filtering IPs, routing low-volume or less critical emails through shared pools to distribute risk, fallback configurations that default to shared IPs when dedicated IPs face issues or limits, and as a protective measure when negative IP reputation affects dedicated IP deliverability.
Key findings
- IP Warm-up: Shared IPs are used to ensure deliverability while dedicated IPs are being warmed up.
- Reporting Errors: SparkPost might report internal filtering IPs instead of actual sending IPs.
- Risk Distribution: Low-volume or less critical emails are sometimes sent through shared IP pools to minimize risk to dedicated IP reputation.
- Fallback Configurations: Emails may default to shared IPs when dedicated IPs experience issues or exceed limits.
- Reputation Protection: Emails might be routed through shared IPs to protect deliverability of dedicated IPs with a negative reputation.
Key considerations
- Monitor IP Warm-up Progress: Track the IP warm-up process to ensure dedicated IPs are being properly ramped up.
- Validate IP Reporting: Confirm the accuracy of IP reporting with SparkPost and investigate discrepancies.
- Review Email Prioritization: Analyze email volume and criticality to determine if routing adjustments can improve deliverability.
- Assess Fallback Settings: Examine fallback settings to understand the conditions under which emails default to shared IPs.
- Manage IP Reputation: Actively monitor and manage IP reputation to prevent deliverability issues on dedicated IPs.
Technical article
Documentation from Amazon SES highlights that fallback configurations in email platforms can result in emails being sent via shared IPs if dedicated IPs experience issues or exceed sending limits.
25 Aug 2023 - Amazon SES
Technical article
Documentation from Google Postmaster Tools shares that negative IP reputation can lead to emails being sent through shared IPs as a protective measure to prevent deliverability issues on dedicated IPs.
25 Apr 2025 - Google
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