Why are my transactional emails delayed when sending from SFMC to Gmail?
Matthew Whittaker
Co-founder & CTO, Suped
Published 9 Aug 2025
Updated 17 Aug 2025
8 min read
Dealing with transactional email delays can be incredibly frustrating, especially when they are critical for your business operations. I often hear from users sending from Salesforce Marketing Cloud (SFMC) to Gmail experiencing lags, sometimes up to an hour, even when using SFMC's Transactional Messaging API. These are not marketing emails, but essential communications like password resets or order confirmations, making timely delivery paramount.
The immediate thought is often a blocklist or poor IP reputation, especially if other ISPs are having issues. However, the situation with Gmail can be more nuanced. While a poor sender reputation can certainly contribute, delays often stem from how Gmail processes incoming mail, or even how the sending platform (SFMC) manages its queues.
In this guide, I will help you understand the common causes of these delays and provide actionable steps to diagnose and resolve them, ensuring your critical emails reach your recipients promptly. We will look at how to troubleshoot significant email delivery delays to Gmail and maintain excellent deliverability.
The nature of transactional email delays
Transactional emails are typically time-sensitive, and any delay can negatively impact user experience and business operations. Unlike marketing emails, which can often tolerate slight delays, transactional messages like account verifications, password resets, or purchase confirmations need to arrive almost instantly. When these messages are slowed, it can lead to customer frustration, support queries, and even lost revenue.
The journey of an email from your SFMC instance to a Gmail inbox involves multiple steps, including your sending platform's servers, various mail transfer agents (MTAs), and finally, Gmail's receiving servers. A delay can occur at any point in this chain, but identifying the exact bottleneck requires careful investigation.
While SFMC aims to provide robust email sending capabilities, shared IP addresses and inconsistent sending practices can sometimes lead to deliverability issues. This is why it's crucial to understand how your email program interacts with major ISPs like Gmail.
Common culprits for delays
One of the most frequent causes of transactional email delays from SFMC to Gmail is related to sender reputation, particularly if you are on a shared IP address. While your domain might not be explicitly blacklisted (or blocklisted) by Gmail, its algorithms might be greylisting or temporarily deferring your emails due to perceived suspicious activity on the shared IP. This often happens if other senders on the same IP are sending low-quality marketing emails or generating spam complaints.
Another factor is the volume and frequency of your sends. Even transactional emails can be subject to throttling by Gmail if they detect unusual spikes or a pattern that resembles bulk sending, especially if the sender reputation is not pristine. Proper email authentication, including SPF, DKIM, and DMARC, plays a crucial role here, as it helps Gmail verify the legitimacy of your emails and trust your sending practices.
IP usage: Ideally sent from dedicated IPs or separate, highly-reputable shared IPs.
Impact on delays: Lower tolerance for delays, higher impact on user experience if throttled.
As outlined in an article by Shift Paradigm on separating email streams, mixing marketing and transactional emails on the same IP is a common pitfall. If marketing sends encounter throttling or deliverability issues, they can unfortunately slow down your critical transactional messages.
Check your email headers
To pinpoint where the delay is occurring, the first step is to examine the full email headers. These headers contain a chronological log of every server the email passed through, along with timestamps.
Locate Headers: In Gmail, open the email, click the three dots next to the reply arrow, and select "Show original" or "Show raw message".
Analyze 'Received:' Lines: Look for lines starting with Received:. Each line indicates a hand-off between servers and includes a timestamp. Compare these timestamps to identify significant gaps.
Decoding email headers and SMTP logs
When you examine your email headers, pay close attention to the Received: lines. These show the time the email was received by each server. If you see a large time gap (e.g., 10+ minutes) between a Salesforce Marketing Cloud (ExactTarget) server and a Gmail server, it indicates a delay either within SFMC's outgoing queues or at Gmail's receiving end.
Example of email headers showing a delayplaintext
Received: from aku6.mta.exacttarget.com (aku6.mta.exacttarget.com. [128.245.242.6])
by mx.google.com with ESMTPS id t14-20020a67f90e000000b00466e83c312dsi395929vsq.692.2024.01.12.05.18.37
for <lhiggins@gmail.com>
(version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128);
Fri, 12 Jan 2024 05:18:37 -0800 (PST)
Received: by aku6.mta.exacttarget.com id hk4u2q2fmd4l for <lhiggins@gmail.com>; Fri, 12 Jan 2024 13:00:05 +0000 (envelope-from <bounce-1355_HTML-51623205-54432-546001304-1@bounce.email.weruva.com>)
In the example above, the SFMC server received the message at 13:00:05 GMT, but Gmail didn't receive it until 05:18:37 PST (which translates to about 13:18:37 GMT). This indicates an 18-minute delay between the SFMC MTA and Gmail. This specific delay could be due to internal queuing at SFMC, or Gmail might have initially deferred (greylisted) the message, requiring SFMC to retry the send later. This is a common tactic Gmail uses to manage inbound mail flow and assess sender legitimacy, as detailed in an article on Stack Overflow regarding Gmail delays.
Delay point
Possible cause
Indicator in headers
SFMC internal queue
High sending volume, resource contention, or specific routing issues within SFMC's infrastructure.
Large time gap between your call to the SFMC API and the first Received: line from SFMC.
Gmail greylisting or throttling
Sender reputation concerns (shared IP issues), high volume spikes, or failure to meet Gmail's sending guidelines.
Large time gap between the last SFMCReceived: line and the first Received: line from Gmail. Might be accompanied by a 4xx temporary error code in SFMC's SMTP logs.
The full SMTP logs from your SFMC account (if accessible) can provide even more granular detail, revealing the exact error codes returned by Gmail during connection attempts. A 4xx code, for instance, confirms a temporary rejection or greylisting, leading to re-queueing and subsequent delays.
Strategies to mitigate delays
Resolving transactional email delays requires a multi-faceted approach. First and foremost, if you are on a shared IP, investigate the possibility of moving your transactional sends to a dedicated IP address. This gives you full control over your sending reputation and isolates your critical emails from the actions of other senders.
Second, ensure your email authentication records are perfectly configured. This includes SPF, DKIM, and DMARC. Gmail and other major ISPs increasingly rely on strong authentication to filter out fraudulent or suspicious emails. Correctly configured records build trust and can significantly improve your deliverability and reduce delays. You can read more about Salesforce's recommendations for authentication.
Best practices for swift delivery
Dedicated IP: Separate your transactional email sending to a dedicated IP, or at least a separate, highly reputable shared IP.
Authentication: Implement robust SPF, DKIM, and DMARC records. Pay attention to DMARC policy enforcement for maximum trust.
Monitoring: Regularly check your Google Postmaster Tools (GPT) dashboard for any reputation issues or delivery errors. GPT offers invaluable insights into how Gmail perceives your sending domain.
Content Quality: Even for transactional emails, avoid spammy content, broken links, or excessive images. Maintain a clean, concise message to avoid triggering spam filters, which can lead to emails being sent to spam or delayed.
Finally, practice good list hygiene. While transactional emails are usually triggered by user actions, maintaining a clean subscriber list (even for one-off sends like password resets) and promptly removing invalid addresses can prevent bounces and further protect your sender reputation. A high bounce rate, even for transactional messages, can negatively impact your deliverability and lead to delays or even blacklisting (or blocklisting) of your IPs.
Proactive monitoring and reputation management
Beyond the technical configurations, consider the overall health of your email program. High complaint rates, even for transactional emails, signal to ISPs like Gmail that your emails might not be wanted, which can lead to delays or outright blocking. Regularly monitor your sender reputation and address any issues promptly. You can refer to our guide on why emails to Gmail experience delivery delays for more insights.
Leveraging tools like Google Postmaster Tools (GPT) is essential. GPT provides valuable data on your sender reputation, spam rates, and delivery errors specifically for Gmail recipients. Regularly reviewing these metrics can help you identify trends and proactively address issues before they escalate into significant delays. Consider a regular email deliverability test to catch problems early.
Views from the trenches
Best practices
Always separate your marketing and transactional email streams onto different IPs or subdomains.
Prioritize transactional email authentication, including robust SPF, DKIM, and DMARC policies.
Actively monitor Google Postmaster Tools for any warnings or reputation declines.
Regularly clean your recipient lists, even for triggered sends, to minimize bounces and complaints.
Common pitfalls
Sending transactional emails from a shared IP with a poor or mediocre marketing reputation.
Ignoring temporary failures (4xx errors) in your SMTP logs, as these indicate greylisting.
Not having full SMTP logs or the ability to retrieve them from your ESP.
Failing to separate marketing and transactional email streams, leading to shared reputation issues.
Expert tips
If you suspect an ESP-side queue, reach out to SFMC support with full email headers and timestamps.
Google Postmaster Tools provides valuable insights into Gmail's perception of your sending domain.
A gradual warm-up is crucial when migrating to new IPs for transactional sends.
Ensure DMARC is set to p=quarantine or p=reject for robust authentication and trust.
Marketer view
Marketer from Email Geeks says they have a client on a mediocre shared IP that is blocked by Hotmail/Outlook, and Gmail is holding onto transactional emails for a really long time, sometimes up to an hour.
Jan 12, 2024 - Email Geeks
Expert view
Expert from Email Geeks says that a common scenario for delays is an initial temporary failure from Google, causing the mail to be re-queued and delivered on a second attempt.
Jan 12, 2024 - Email Geeks
Ensuring prompt transactional email delivery
Transactional email delays to Gmail, particularly from SFMC, are often a symptom of broader deliverability challenges rather than a simple blocklist issue. By carefully analyzing email headers, understanding the nuances of IP reputation, and implementing robust authentication practices, you can significantly reduce these delays. Proactive monitoring through tools like Google Postmaster Tools is key to maintaining a healthy sender reputation and ensuring your transactional emails always arrive promptly.
Salesforce Marketing Cloud (SFMC) to 
Gmail experiencing lags, sometimes up to an hour, even when using SFMC's Transactional Messaging API. These are not marketing emails, but essential communications like password resets or order confirmations, making timely delivery paramount.
Gmail, open the email, click the three dots next to the reply arrow, and select "Show original" or "Show raw message".
SFMC's infrastructure.
