What is a safe percentage to increase email volume when sending from SFMC?
Michael Ko
Co-founder & CEO, Suped
Published 24 Apr 2025
Updated 17 Aug 2025
7 min read
Increasing email volume can feel like walking a tightrope, especially when dealing with platforms like Salesforce Marketing Cloud (SFMC). My company has managed a consistent volume of around 3 million emails per month from our SFMC IPs since 2019, targeting a mix of client and major inbox provider domains like Google and Yahoo. Now, with requests for large, standalone campaigns exceeding 4 million recipients, the prospect of a significant volume spike brings back concerns about deliverability ramifications.
The core challenge lies in balancing the need to send more emails with maintaining a healthy sender reputation. Internet Service Providers (ISPs) closely monitor sending behavior, and sudden, drastic increases in volume can trigger their spam filters, leading to emails landing in the junk folder or even being blocked entirely. This is why a strategic approach to scaling email volume is crucial.
I'm always working with stakeholders to optimize audiences and throttle sends, but the question remains: what percentage increase in email volume is considered safe, and at what point does it become unsafe? This guide explores the factors that influence these thresholds and offers practical advice for managing email volume increases effectively.
Understanding email volume and sender reputation
Sender reputation is the bedrock of email deliverability, and it's built over time through consistent, positive sending behavior. ISPs (Internet Service Providers) track various metrics, including volume, bounce rates, complaint rates, and engagement. Any abrupt change in these patterns can be perceived as suspicious, much like an unfamiliar car suddenly speeding through a quiet neighborhood. This is particularly true if you are on dedicated IP addresses, where your sending history is directly tied to a specific IP or set of IPs.
A sudden surge in email volume, without proper IP warming strategies, can lead to several negative outcomes. Firstly, your emails might bypass the inbox and land directly in spam folders. Secondly, your sending IP address could be placed on an email blocklist (or blacklist), preventing delivery altogether. Lastly, a hit to your sender reputation can take considerable time and effort to recover from.
For established senders like us, with multiple dedicated IPs, the risk isn't as high as for a brand new sender, but caution is still paramount. The key is to implement a gradual increase, a process commonly referred to as IP warming or re-warming. This allows ISPs to gradually get accustomed to the higher volume coming from your IPs, ensuring your mail streams are not flagged as unusual or malicious.
Strategies for safe volume increases
When considering how much to increase your email volume, the general consensus among deliverability experts points towards a conservative, gradual ramp-up. A safe increase typically falls within the 10-20% range of your average daily or weekly sending volume. For example, if you send 100,000 emails per day, an increase to 110,000 or 120,000 would be a reasonable next step.
Recommended increase
A good rule of thumb for established sender reputation is to increase your volume by no more than 10-20% per day or per send cycle. This allows mailbox providers to adjust to your sending patterns without triggering spam filters. When you are doing an initial IP warming, you might be able to go higher depending on the quality of your list and engagement.
Audience segmentation
When planning a volume increase, prioritize your most engaged subscribers. Sending to a highly responsive segment first helps maintain positive engagement rates, which are critical for convincing ISPs that your mail is wanted. Avoid sending to unengaged users or older segments during a ramp-up.
The safety of a percentage increase is not solely about the number itself, but also about the context. Factors like the diversity of your recipient domains, the overall engagement of your list, and the consistency of your content all play significant roles. For example, sending a 15% increase to a highly engaged list of primarily Salesforce Marketing Cloud customers is far safer than a 5% increase to an old, unsegmented list.
Gradual scaling
Process: Increase volume incrementally, e.g., 10-20% daily or weekly, focusing on consistent growth.
Reputation: Maintains a positive sender reputation and builds trust with mailbox providers over time. This approach reduces the risk of being perceived as a spammer.
Deliverability: Optimizes inbox placement and minimizes the chances of hitting spam folders or getting blocklisted.
Rapid scaling (unsafe)
Process: Sudden, large increases in sending volume without a warming period.
Reputation: Can severely damage sender reputation, leading to immediate scrutiny by ISPs. This can result in your IP or domain being flagged as suspicious.
Deliverability: High likelihood of emails being blocked, throttled, or routed to spam, significantly impacting campaign performance. Recovery can be a prolonged process.
Navigating SFMC for high-volume sending
Salesforce Marketing Cloud provides robust infrastructure, but it's essential to understand its capabilities and limitations regarding email volume. While SFMC itself doesn't typically throttle your sending rate if you exceed general guidelines, your sender reputation with ISPs is what truly dictates deliverability. If you have multiple dedicated IPs within your SFMC instance, spreading the increased volume across them can mitigate risk, as each IP maintains its own reputation.
Example volume ramp-up schedule
Week 1: 50,000 emails/day
Week 2: 100,000 emails/day
Week 3: 200,000 emails/day
Week 4: 400,000 emails/day
Week 5+: Gradually increase by 10-20% weekly as long as metrics are stable
For significant volume spikes, consider leveraging SFMC's features like High-Throughput Sending (HTS) where applicable, which is designed for higher volume. Also, focus on sending to your most engaged subscribers first. This practice, known as prioritizing engaged users, signals positive behavior to ISPs and can help absorb the initial impact of increased volume. Always consult with Salesforce's deliverability support for tailored advice specific to your account configuration and sending history.
The foundation of safe volume increases within SFMC, or any platform, hinges on the quality of your subscriber list. A clean, engaged list naturally supports higher sending volumes because it generates positive interactions, reducing the risk of bounces and complaints. Regularly cleaning your list and removing unengaged or invalid addresses is a non-negotiable best practice.
Monitoring key metrics
During any period of increased email volume, rigorous monitoring of key deliverability metrics is non-negotiable. Pay close attention to your bounce rates, particularly hard bounces, which indicate invalid email addresses and can quickly damage your reputation. Keep an eye on complaint rates, as high complaint rates (users marking your email as spam) are a strong negative signal to ISPs.
Engagement metrics, such as open rates and click-through rates, provide positive signals. If these metrics start to decline significantly during a volume increase, it could indicate that your messages are not reaching the inbox or are not resonating with your audience. Sustaining high engagement is crucial, especially when you are scaling your sending operations.
Metric
Acceptable Threshold
Action if Exceeded
Bounce rate
Below 2%
Immediately clean your list; investigate poor data quality.
Complaint rate
Below 0.1%
Review content, segmentation; make opt-out easier.
Open rate
Varies by industry, aim for consistent or improving rates.
Optimize subject lines, preheaders; improve list engagement.
Blacklist status
Zero listings
Immediately check your IP and domain against major blocklists.
Beyond these, keep a close watch on your DMARC reports. They provide invaluable insight into authentication failures, which can be exacerbated by sudden volume shifts. Any sign of declining deliverability or rising negative metrics during a volume increase should prompt a pause and reassessment of your sending strategy.
Red flags for email deliverability
A bounce rate consistently above 5% or a complaint rate above 0.2% can dramatically impact your sender reputation and lead to serious deliverability issues, especially with high-volume sending. These thresholds indicate significant problems with list hygiene or content relevance, and require immediate attention.
Views from the trenches
Best practices
Start with smaller, highly engaged segments of your audience to establish a positive sending pattern before scaling up to larger, less engaged segments.
Always maintain a clean email list by regularly removing inactive subscribers, hard bounces, and any known spam trap addresses.
Continuously monitor your deliverability metrics, including open rates, click-through rates, bounces, and complaints, during any volume increase.
Common pitfalls
Attempting to send a significantly large campaign to an unengaged or old list without prior re-engagement, which can lead to high bounces and spam complaints.
Ignoring early warning signs from deliverability metrics, such as a slight increase in bounce rates or a dip in engagement, thinking they will self-correct.
Not segmenting your audience and sending large volumes to all recipients simultaneously, which can dilute positive engagement signals.
Expert tips
Consider pacing your sends over several days for exceptionally large campaigns instead of a single massive burst, to smooth out volume spikes.
Leverage SFMC's High-Throughput Sending (HTS) if available and appropriate for your campaigns, but always combine it with careful list management and monitoring.
For very high-volume senders, review your email content and sending practices to ensure they align with the latest Google and Yahoo bulk sender requirements.
Marketer view
Marketer from Email Geeks says a 10% increase spread over three dedicated IPs would easily be fine, provided there are no dramatic changes to content or recipient types.
2023-08-09 - Email Geeks
Expert view
Expert from Email Geeks says when warming up, an increase of up to 50% per day can be achieved, but this is typically for initial warming, not established sending.
2023-08-09 - Email Geeks
Navigating volume increases successfully
Safely increasing email volume in Salesforce Marketing Cloud is a nuanced process that demands a strategic and data-driven approach. While specific percentage increases like 10-20% per cycle serve as a good starting point, the ultimate safety threshold depends heavily on your unique sending history, list hygiene, and the engagement levels of your audience.
The key is to always err on the side of caution, prioritizing the health of your sender reputation over rapid volume expansion. By consistently monitoring your metrics, segmenting your audience intelligently, and gradually scaling your sends, you can effectively manage increased volume and ensure your emails continue to reach the inbox, maximizing the impact of your campaigns.
Yahoo. Now, with requests for large, standalone campaigns exceeding 4 million recipients, the prospect of a significant volume spike brings back concerns about deliverability ramifications.
Salesforce's deliverability support for tailored advice specific to your account configuration and sending history.
