Does Email Warmup Work? Evidence, Tests, and How to Prove It

Does email warmup work? Quick answer: Yes (with caveats)

Email warmup works, but only if done right. When you gradually ramp up sending volume, interact with engaged recipients, and avoid detectable patterns, you build reputation and boost inbox placement. The CEO of Hailo Digital Agency consistently saw open rates climb from 35% to over 90% with proper warmup, avoiding spam filters and blocklists.

However, debates rage in places like community forums. Some users share success stories, especially for new domains, while others warn about the risks associated with shared warmup pools and automated, bot-like behaviors.

Why is Email Warmup Controversial?

Email warmup helps with better deliverability, but people have mixed opinions about it. Let’s look at how warmup helps and why it’s sometimes debated.

How Does Email Warmup Help?

Email warmup builds trust with inbox providers by starting with low sending volumes and slowly increasing them. This confirms your domain and IP are legitimate. For example, one of MailReach users doubled its open rates and cut bounce rates by focusing on verified contacts and authentic engagement like opens, clicks, and replies.

Another aspect which is important for new domains with no sending history whatsoever is, sending first to engaged contacts since it helps cut bounce rates and spam complaints. 

Common Criticisms and Risks

All email warmers operate within networks where your warmup activity interacts with mailboxes from other users. Because of this shared environment, your sender reputation can be influenced by the overall behavior within the network.

That being said, a key point to keep in mind is where your warmup interactions come from. Many networks mostly rely on custom SMTP servers instead of major providers like Gmail or Outlook. Since Gmail and Outlook carry more weight in building sender reputation, getting positive engagement from them really matters. Interactions from custom SMTPs just don’t build trust with major inbox providers the same way.

On top of that, automated or artificial engagements come with risks because email providers can spot inauthentic activity and may penalize your account or affect where your emails land.

Also, sending too many emails too fast during warmup can set off spam filters, making your messages go to spam or get blocked, which can hurt your domain’s reputation.

In the end, if warmup isn’t done right, it can be ineffective or even damage your sender reputation. Taking it slow with real engagement from trusted contacts is the best way to go.

What Email Providers and Deliverability Experts Recommend?

Experts like Georgey Tishin agree that proper warmup, with slow volume growth, real engagement, and no shady automation, is key to good deliverability and inbox placement.

When you start with a new domain or mailbox, warming up gradually and following careful practices is key to building your sender reputation and getting into inboxes.

Think of your email domain like a new person joining a community. You wouldn’t start by sending messages to hundreds of strangers right away. Instead, you’d introduce yourself slowly, build genuine connections, and earn trust over time.

Don’t believe us? Let’s hear from top companies and experts.

Microsoft recommends starting with low email volumes and increasing slowly over several weeks. They also stress the importance of setting up SPF, DKIM, and DMARC to authenticate your domain. Checking bounce rates and spam complaints helps adjust your sending habits.

Google advises sending first to engaged recipients to create positive signals such as opens and clicks. Its Postmaster Tools help you track your domain and IP reputation and spot issues early. This is ideal for high volume senders. For B2B, use MailReach’s reputation score to build send reputation. 

Mailreach’s email warmup trends highlight the importance of warming up new IPs and domains using AI, real-time monitoring and focused engagement to maximize deliverability.

Best Practices for Safe and Effective Warmup

• Set up SPF, DKIM, and DMARC before sending to prove your domain’s legitimacy. Tools like SPF/DKIM checker help verify proper setup before starting warmup.
• Don’t send any campaigns during the first 14 days of a domain / IP
• Stay under 100 daily sends per inbox for B2B cold outreach
• Start with low volume (2–4 emails/day) for 3-4 weeks and increase gradually by 10–20 emails every few days. You can also use an email warmup tool like MailReach to automate this process for you.
• Keep a consistent sending pattern. Avoid spikes or long gaps
• Use useful and clear content to avoid email spam filters.
• Monitor reputation daily using MailReach’s reputation score
• Automate warmup with real recipient engagement using tools like MailReach
• Use real-time alerts to catch and fix deliverability issues fast
• Continue warmup beyond the initial phase to maintain reputation

How to Measure Warmup Impact 

To know if your email warmup is working, track the right metrics. The best way to do this is by running a spam test, a real inbox placement test that matches the conditions of your actual campaigns. 

This shows exactly where your emails land: inbox, spam, or promotions. Running the test under real campaign conditions gives you a true picture of how email providers handle your messages.

MailReach’s free Spam Test is a great tool for this. It gives a clear view of inbox placement and spam score in one test, helping you spot issues and know what to fix to improve deliverability.

Besides the spam test, watch these key metrics:

• Inbox placement rate: The percentage of emails that land in the inbox instead of spam. Some users have improved this from 40% to 75% in just two weeks of warming up
• Bounce rate: The percentage of emails that don’t deliver. Keep this below 4%, since a high bounce rate usually points to poor list quality or sending too fast
• Sender reputation score: If you’re doing B2B, MailReach’s Reputation Score helps you track your domain and IP reputation in real time

Step-by-Step Reproducible Test You Can Run

You can run a 14-day email warmup test to steadily build your sender reputation and measure its impact. Here’s how to do it using a proven warmup schedule.

• Create a new email account or domain
• Set up SPF, DKIM, and DMARC authentication before sending any emails
• Use a verified, engaged contact list
• Follow a controlled volume increase schedule: warm up over 14 days with gradual increases, then start sending 50 emails per day on day 15
• After day 15, increase the daily send volume by 20 emails per day
• Track inbox placement, bounce rate, spam complaints, engagement, sender reputation scores, and blocklist status.

Avoid exceeding 100 emails/day per inbox for B2B cold email.

14-Day Warmup Calendar Example

Following this schedule with close monitoring helps prove email warmup’s impact and prepares your domain for larger volumes safely.

Bonus share: Tools like MailReach automate this process, generating authentic engagement (opens, replies) with people to build authentic trust over time. It also helps monitor metrics in real time to adjust your warmup strategy and protect your reputation.

How MailReach Approaches Warmup Differently

MailReach’s prime feature is its Email Warmup. It automatically warms your email by sending real, positive interactions with trusted inboxes. This builds your sender reputation fast and keeps your emails out of spam. The tool:

• Uses automated peer-to-peer exchanges with 30,000+ real inboxes like Google Workspace and Office 365
• Automates realistic conversations between MailReach users
• Sends emails that get opened, replied to positively, marked as important, and removed from spam
• Trains inbox providers like Google and Microsoft to place your future emails in the inbox
• Follows a safe volume ramp-up with gradual increases
• Provides real-time reputation monitoring and Slack alerts
• Uses varied, natural email content
• Offers an account health overview by domain, tag, and provider
• Works smoothly with all SMTP providers, including Gmail, Outlook, Zoho, and Amazon SES

This is an example of a warming email generated by MailReach.

And a typical reply is

All these emails are automated to build trust with Google and Microsoft. 

Warmup with MailReach. Learn more.

Warmup Readiness Checklist Before Starting Outreach

Run your email warmup for B2B outreach and debunk the myths yourself. Click here.