Why are Gmail emails delayed after migrating to SFMC, and how can I fix it?
Matthew Whittaker
Co-founder & CTO, Suped
Published 10 Jul 2025
Updated 17 Aug 2025
6 min read
Migrating email operations to a new platform like Salesforce Marketing Cloud (SFMC), especially with a new subdomain and shared IP address, can sometimes lead to unexpected delivery challenges. One common issue is experiencing significant delays for emails sent to Gmail recipients. While it might seem alarming, particularly when your emails are eventually delivered, it often signals that Gmail is carefully evaluating your new sending patterns and reputation.
Even with a seemingly smooth, brief warm-up phase and initial good engagement, these delays, sometimes lasting up to 24 hours, can severely impact your campaign performance and overall subscriber experience. Understanding the underlying reasons for these delays is crucial for restoring consistent and timely email delivery to Gmail.
Understanding the nature of email delays
When Gmail holds emails before releasing them, it is a strong indicator of an active reputation assessment. This is especially true for new sending infrastructures. During this period, Gmail monitors how a subset of recipients interacts with your mail before allowing the rest through. It is a cautious approach designed to protect their users from potential spam or unwanted mail, which applies even to legitimate senders establishing new sending identities.
It is important to distinguish between Gmail holding emails and your Email Service Provider (ESP) deferring them. While some delays can occur due to deferred messages queuing on the sending side, if your email headers show a significant gap between when Gmail accepts the mail and when it lands in the user's inbox, the delay is indeed on their end. Mailbox providers typically avoid extensive queuing on their side because it can be resource-intensive.
The primary factor at play here is sender reputation. A new subdomain, even one associated with a well-established primary domain, starts with little to no reputation in the eyes of mailbox providers like Gmail. Being on a shared IP address means your sending reputation is also influenced by other senders on that same IP, adding another layer of complexity. This initial lack of trust leads ISPs to exercise caution and implement delays.
Common causes of post-migration delays
A brief warm-up for a new subdomain and shared IP is often insufficient, even with low daily volumes. The goal of a warm-up is to gradually build trust with ISPs by demonstrating consistent, positive sending behavior. If you increase volume too quickly, Gmail may interpret this as suspicious, leading to delays or even outright blocking.
Inadequate warm-up
New subdomain: Starts with zero reputation, regardless of your primary domain's history.
Shared IP: Reputation is influenced by all senders using that IP. If others have issues, it can affect you.
Rapid volume increase: Even for existing customers, a sudden jump in volume from a new source can trigger filters.
It is also possible that the concurrent sending from your old ESP, even if it uses your primary domain, might create a perceived inconsistency, especially if authentication records are not perfectly aligned. While some experts suggest this may not be a direct cause of delays, maintaining a clean and unified sending setup is generally a best practice.
Strategic warm-up and list hygiene
The most effective way to resolve delays is to adjust your sending volume to a rate that Gmail is willing to accept. This often means scaling back until delays subside, and then gradually increasing again. Think of warm-up as sending mail slower than the ISP wants to take it, gradually increasing as trust is built. A multi-month period for full stabilization, especially after a significant migration, is not uncommon.
Current approach
Brief warm-up: A week or less, not considering the new subdomain's lack of reputation.
Sending to all customers: Even loyal customers can appear suspicious when receiving emails from a new, unproven sender.
Focus on high volume: Prioritizing throughput over gradual trust-building can trigger delays.
Recommended adjustment
Extended warm-up: Plan for 4-12 weeks, gradually increasing volume based on engagement.
Engaged segments first: Start by sending to your most active subscribers on the new setup.
Observe and adapt: Monitor delivery metrics and adjust sending speed based on ISP feedback.
Beyond warm-up, focus on maintaining a clean email list and strong engagement. Continue to validate email addresses regularly to keep bounce rates low. Low bounce rates are a key signal of list health. Additionally, encouraging your subscribers to add your new sending address to their contacts or safe sender list can provide a direct positive signal to Gmail.
Monitoring and advanced troubleshooting
The primary tool for monitoring your domain's reputation with Gmail is Google Postmaster Tools. While data can sometimes be limited, it provides crucial insights into your domain and IP reputation, spam rate, and authentication errors (SPF, DKIM, DMARC). A consistently high reputation and 0% spam complaints are good signs, but persistent delays suggest that Google is still in a cautious evaluation phase. You can also refer to our guide to Google Postmaster Tools for more detailed information.
Ensure your email authentication protocols are correctly configured for your new SFMC setup. This includes SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance). Incorrect or missing records can signal a lack of legitimacy to ISPs, leading to delays and spam placement. You can use a free DMARC record generator to ensure proper setup. The recent bulk email restrictions from Google and Yahoo emphasize authentication, one-click unsubscribe, and a low spam complaint rate.
Moving forward to consistent deliverability
Experiencing email delays, especially after a migration to a new platform like SFMC, is a common scenario. It can be frustrating when your messages, despite eventually being delivered, arrive at unpredictable times. This often results in a noticeable dip in engagement rates, as your audience might receive communications at non-optimal times, or simply lose interest due to the inconsistent delivery experience.
The key is to approach this challenge with patience and a data-driven strategy. While it may take 2-3 months for your new sending infrastructure to stabilize fully in the eyes of major ISPs like Gmail, consistent application of best practices will accelerate the process. Focusing on a proper warm-up, maintaining a highly engaged list, and leveraging monitoring tools are essential steps. By understanding that these delays are often a form of cautious evaluation, you can respond strategically to build the necessary trust for optimal deliverability.
Views from the trenches
Best practices
Implement a slow and steady warm-up process tailored to your audience engagement, rather than just volume.
Segment your audience and prioritize sending to your most active and engaged subscribers first during the warm-up phase.
Proactively ask your subscribers to add your new 'from' address to their contacts or safe sender lists.
Common pitfalls
Assuming a brief, one-week warm-up is sufficient for a new subdomain and shared IP address.
Ignoring email header analysis to determine if delays are client-side or caused by the ESP's deferrals.
Sending at too high a volume too quickly, triggering cautious filtering from mailbox providers.
Expert tips
Email Geeks experts confirm that if Gmail is holding and then releasing, they are likely watching recipient behavior.
One expert advises checking SMTP responses for deferral messages to understand where queuing is happening.
An expert notes that mailbox providers usually avoid queuing emails on their end because it's resource intensive.
Expert view
Expert from Email Geeks says if Gmail is holding and then releasing emails, they are likely watching a subset of recipients to see how they interact with your mail before allowing the rest through. It is important to stay the course.
2024-01-31 - Email Geeks
Expert view
Expert from Email Geeks says the queuing is typically on the sending side, as it is expensive for mailbox providers to queue emails on their receiving side.
Gmail. Being on a shared IP address means your sending reputation is also influenced by other senders on that same IP, adding another layer of complexity. This initial lack of trust leads ISPs to exercise caution and implement delays.
Gmail.
