Summary
Emails sent from Marketing Cloud on a shared IP can be delayed despite proper authentication due to a complex interplay of factors. A primary culprit is the shared IP's reputation, which is influenced by the sending behavior of all users on that IP. Poor sending practices by others, such as sending spam or triggering spam traps, can negatively impact deliverability, leading to delays, throttling, or even blacklisting, regardless of your authentication efforts. Technical issues such as improperly configured PTR records, SFMC's internal delays or Gmail deferrals, recipient mail server load, and email content triggering spam filters can also contribute to delays. New Marketing Cloud accounts or those sending significantly increased email volumes need to implement IP warming strategies to establish a positive sending reputation. Monitoring IP reputation, maintaining low spam rates, and ensuring proper email authentication are crucial for timely email delivery.
Key findings
- Shared IP Reputation is Key: The reputation of a shared IP is paramount. Poor sending practices by other users on the same IP can negatively affect your deliverability.
- Multiple Potential Delay Causes: Delays can stem from various sources, including SFMC internal issues, Gmail deferrals, improperly configured PTR records, or the recipient's mail server load.
- Impact of Spam Filters: Email content that triggers spam filters can cause delays, even with proper authentication.
- Importance of IP Warming: New IPs or those sending increased volumes need to be 'warmed up' to establish a positive sending reputation.
- Blacklisting Risks: Blacklisting of shared IPs can occur due to the actions of other senders, leading to significant delivery delays.
Key considerations
- Monitor IP Reputation: Actively monitor your shared IP's reputation to identify and address any potential issues affecting deliverability.
- Optimize Email Content: Ensure your email content avoids triggering spam filters and aligns with best practices to maintain good engagement.
- Verify Authentication Setup: Regularly check that SPF, DKIM, and DMARC records are correctly configured and validated to ensure robust authentication.
- Implement IP Warming Strategy: When starting with a new IP or significantly increasing email volume, follow a gradual IP warming strategy.
- Consider a Dedicated IP: If persistent deliverability problems occur, consider switching to a dedicated IP address to have more control over your sending reputation.
What email marketers say
10 marketer opinions
Emails sent from Marketing Cloud on a shared IP can experience delays despite proper authentication due to several factors. The most prominent reason is the shared IP's reputation, which is influenced by the sending behavior of all users on that IP. If others send spam or have poor email practices, it negatively impacts deliverability, leading to delays and throttling by ISPs. Other factors include issues with PTR record configuration, recipient server load, email content triggering spam filters, and the need for IP warming to establish a positive sending reputation.
Key opinions
- Shared IP Reputation: A shared IP's reputation is determined by the collective sending practices of all its users. Poor practices by others can negatively affect your deliverability, causing delays.
- PTR Record Configuration: Improperly configured PTR records can cause delays. Ensuring PTR records are correctly associated with the sending domain is crucial.
- ISP Throttling: ISPs may throttle emails from shared IPs with a history of spam or low engagement, causing delays even with proper authentication.
- Email Content: Email content that triggers spam filters can lead to delays, even when authentication is properly configured.
- IP Warming: New IPs, or those with significantly increased email volume, need to be 'warmed up' to establish a positive sending reputation with ISPs, preventing delays.
Key considerations
- Monitor IP Reputation: Regularly monitor your shared IP's reputation to identify and address any issues that may arise.
- Optimize Email Content: Ensure your email content is optimized to avoid triggering spam filters and maintain good engagement.
- Consider Dedicated IP: If deliverability issues persist, consider switching to a dedicated IP address to have full control over your sending reputation.
- IP Warming Strategy: If starting on a new IP, establish a gradual IP warming strategy, slowly increasing sending volume over time.
- Authentication Verification: Confirm that SPF, DKIM, and DMARC records are properly configured and validated to ensure strong authentication.
Marketer view
Email marketer from StackExchange explains that when using a shared IP address and a shared hosting provider, there could be an issue in the configuration, or the hosting provider's IP address may already be blacklisted from sending spam emails. Thus, your authenticated emails may be delayed or never delivered at all.
20 Aug 2021 - StackExchange
Marketer view
Email marketer from Neil Patel Blog explains that using a shared IP address for email marketing can lead to deliverability issues, even with proper authentication, because your email reputation is tied to other users on that IP. If they send spam or have poor email practices, it can negatively affect your deliverability.
11 Jun 2025 - Neil Patel Blog
What the experts say
7 expert opinions
Emails sent from Marketing Cloud on a shared IP can be delayed despite proper authentication primarily due to factors outside of immediate sender control. Examining email headers is the first diagnostic step. Potential causes include SFMC internal delays, Gmail deferrals (often due to shared IP issues), and overall IP reputation problems stemming from other users on the same IP sending practices. Even with proper authentication, a poor shared IP reputation (due to other senders) can significantly impact deliverability, causing delays or filtering. It's also important to note that while SPF misalignment isn't ideal, it is acceptable as long as DKIM is aligned. Since SFMC doesn't readily provide deferral tracking to clients, contacting their support may be necessary to investigate specific delivery issues.
Key opinions
- Examine Email Headers: The first step in troubleshooting email delays is to examine the email headers to pinpoint where the delay occurred.
- SFMC/Gmail Deferrals: Delays can originate from SFMC internal issues or Gmail deferrals. SFMC support should be able to provide deferral reasons.
- Shared IP Reputation is Key: Even with perfect authentication, the shared IP's overall reputation has a profound impact on deliverability. Actions of other senders on the same IP are impactful.
- SFMC Deferral Tracking: SFMC does not readily track deferrals in a way clients can easily access; direct support contact is often needed for in-depth analysis.
- SPF/DKIM Alignment: SPF misalignment is acceptable as long as DKIM is aligned, however best practice to resolve SPF misalignment where possible.
Key considerations
- Monitor IP Reputation: Continuously monitor the reputation of your shared IP address to identify and mitigate any potential issues.
- Contact SFMC Support: Engage with SFMC support to investigate specific instances of email delays and understand the underlying causes within their platform.
- Review Sending Practices: Ensure your email practices are in line with best practices to avoid negatively impacting the shared IP's reputation.
- Authentication Check: Regularly verify that your SPF, DKIM, and DMARC records are correctly configured and functioning to maximize email deliverability.
- Investigate Header Information: Learn to analyze email headers effectively to identify points of delay and potential causes.
Expert view
Expert from Email Geeks explains that the full headers show that SFMC sent the email, but Gmail deferred it, suggesting Gmail deferrals as the issue. He recommends checking SFMC reporting or contacting SFMC support.
8 Dec 2021 - Email Geeks
Expert view
Expert from Email Geeks suggests that the issue smells like Gmail deferrals, mentioning that SFMC doesn't track deferrals in a way accessible to clients. Shared IP + Gmail issues in that scenario is kind of a tough way to go.
15 Aug 2024 - Email Geeks
What the documentation says
4 technical articles
Emails sent from Marketing Cloud on a shared IP may be delayed despite proper authentication due to several technical and reputational factors. The reputation of a shared IP is determined collectively by all users sharing that IP, and poor sending practices by others can negatively impact your deliverability, potentially leading to blacklisting and delays. High spam rates, even with authentication, can also trigger filtering and delays. Furthermore, email transfer agents (MTAs) prioritize email delivery and may delay messages until they are confident of successful delivery, especially if technical issues arise. New Marketing Cloud accounts or accounts with significantly increased volume should implement IP warming strategies.
Key findings
- Shared IP Reputation: The reputation of a shared IP is collectively determined by all users, influencing email deliverability.
- High Spam Rates: Elevated spam rates lead to delays and filtering, even with proper email authentication.
- IP Blacklisting: Actions of other senders on a shared IP can result in blacklisting, causing delays regardless of your authentication efforts.
- MTA Prioritization: Email transfer agents (MTAs) prioritize email delivery and may delay messages until service is restored or success is ensured.
- IP Warming is Essential: New Marketing Cloud accounts or those sending increased volumes need to warm up their IP to build a positive reputation.
Key considerations
- Monitor Spam Rates: Vigilantly monitor and maintain low spam rates to ensure timely delivery and avoid filtering.
- Implement IP Warming: Adopt a gradual IP warming strategy when starting with a new IP or significantly increasing email volume.
- Review Sending Practices: Regularly review and optimize your email sending practices to avoid negatively impacting the shared IP's reputation.
- Authenticate Properly: Ensure all email authentication protocols (SPF, DKIM, DMARC) are correctly configured and functioning.
- Address Blacklisting Issues: If blacklisting occurs, promptly identify the cause and take corrective actions to restore IP reputation.
Technical article
Documentation from SparkPost Help explains that blacklisting of shared IPs can occur due to the actions of other senders using the same IP. This can lead to significant delivery delays and blockages, regardless of your own authentication efforts.
7 Jul 2021 - SparkPost Help
Technical article
Documentation from RFC Editor shares that email message transfer agents (MTAs) have different priorities when handling and delivering emails. When a problem arises, they may delay messages until the service is restored or until they are confident they can deliver the email successfully.
14 Jan 2024 - RFC-Editor
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