Table of Contents
What is Email Warmup?
Email warmup is the process of gradually increasing the sending volume of a new or inactive email account to build a positive sender reputation with email service providers (ESPs) like Google, Microsoft, and Yahoo.
When you create a new email account and immediately start sending 500 cold emails per day, email providers flag your behavior as suspicious. Their algorithms are trained to detect spam, and sudden high-volume sending from an account with no history is a textbook spam signal.
Warmup solves this by mimicking organic email growth. You start with a small number of emails, gradually increase over weeks, and prove to ESPs that your account behaves like a legitimate human sender.
Simple analogy: Think of your email reputation like a credit score. New accounts start with zero history. You have to build a track record of good behavior — sending, receiving, opening, and replying — before lenders (email providers) trust you with higher limits.
Why You Absolutely Need Email Warmup
The consequences of skipping warmup are severe and sometimes permanent. Here is what happens when you send cold email from an unwarmed account:
- Immediate spam placement — 80-100% of emails go to spam folders
- Domain blacklisting — your domain gets added to email blacklists
- Account suspension — Google and Microsoft will suspend accounts sending suspicious volume
- Permanent reputation damage — some domain reputations cannot recover
- Wasted leads — you burn through your prospect list with zero results
Real scenario: A marketer sends 1,000 cold emails from a brand new Gmail account on day one. Google detects the pattern, suspends the account within 24 hours, and the domain gets flagged. Even after creating a new account on the same domain, emails continue going to spam. The domain is essentially unusable for cold outreach.
Before You Start Warming Up
Warmup only works if your technical foundation is correct. Complete these steps before starting warmup:
Configure SPF Record
Add a TXT record authorizing your mail provider to send on behalf of your domain.
Enable DKIM Signing
Enable DKIM in your email provider settings and add the CNAME records to your DNS.
Set Up DMARC
Add a DMARC TXT record with p=none to start monitoring email authentication.
Age Your Domain
New domains under 30 days old have very low trust. Register domains 30-90 days before warming up.
Check your setup: Use MXToolbox.com or mail-tester.com to verify your SPF, DKIM, and DMARC records are configured correctly before starting warmup.
The Optimal Warmup Schedule
The key principle of warmup is gradual, consistent growth. Here is a proven 8-week warmup schedule that works across all major email providers:
| Week | Emails Per Day | Open Rate Target | Reply Rate Target | Notes |
|---|---|---|---|---|
| Week 1 | 3-5 | 80%+ | 20%+ | Only send to trusted contacts or warmup pools |
| Week 2 | 8-12 | 70%+ | 15%+ | Mix real and warmup emails |
| Week 3 | 15-20 | 65%+ | 15%+ | Start checking spam scores |
| Week 4 | 25-30 | 60%+ | 10%+ | Good time to send first test campaign (small batch) |
| Week 5 | 35-40 | 55%+ | 10%+ | Scale up gradually |
| Week 6 | 45-50 | 50%+ | 8%+ | Ready for regular cold outreach |
| Week 7-8 | 60-80 | 45%+ | 8%+ | Full campaign mode, keep warming running in background |
Important: Never stop warmup completely even after you start campaigns. Keep 20-30% of your daily sending quota for warmup emails. This maintains your reputation while your campaign emails go out.
Automating Warmup with NexusSender
Manual warmup is tedious and error-prone. NexusSender includes a built-in warmup engine that automates the entire process — sending, opening, and replying between your warmup accounts without any manual intervention.
How NexusSender Warmup Works
- You add your email accounts to the warmup pool (SMTP credentials)
- NexusSender sends emails between accounts on a randomized schedule
- Emails are automatically opened to signal positive engagement
- The system gradually increases daily volume following the ramp settings you configure
- A cron job runs every 5 minutes to manage the warmup queue automatically
Warmup Configuration in NexusSender
For each account you add to warmup, configure these settings:
- Start: Emails per day to begin with (recommended: 3-5)
- Increase: How many more emails to add per day (recommended: 2-3)
- Max: Maximum emails per day to reach (recommended: 40-50)
- Ramp Day: Automatically tracked as warmup progresses
Best practice: Add at minimum 3-5 accounts to your warmup pool. Accounts warm up by exchanging emails with each other — more accounts means more realistic-looking traffic patterns and faster reputation building.
7 Warmup Mistakes That Destroy Deliverability
-
Starting campaigns before warmup is complete
The most common mistake. Even if you feel impatient, wait the full 4-6 weeks. Starting too early undoes all warmup progress. -
Using a brand new domain
Domains need time to age. A domain registered today has near-zero trust. Register your sending domains at least 30 days before you need them. -
Skipping DNS configuration
No SPF, DKIM, or DMARC means your emails fail authentication checks before even reaching the inbox. Always configure these first. -
Warmup volume jumping too fast
Going from 5 to 50 emails overnight triggers spam filters. Follow the gradual schedule above — steady consistent growth only. -
Only warming up once
Warmup is not a one-time event. Run warmup continuously in the background even when you have an established account. A 2-week pause followed by heavy sending can reset your reputation. -
Using the same email content for warmup
If all warmup emails are identical, ESPs detect the pattern. Use varied subject lines and body content — NexusSender automatically varies warmup email content. -
Not monitoring spam placement
Warmup without monitoring is flying blind. Use GlockApps or Mail-Tester weekly to check where your emails are landing.
How to Test Your Sender Reputation
Use these free tools to check your email health throughout the warmup process:
- Mail-Tester.com — sends a test email and scores your deliverability from 1-10. Aim for 9+.
- MXToolbox.com — checks your DNS records, blacklist status, and SMTP configuration
- GlockApps.com — tests inbox placement across Gmail, Outlook, Yahoo, and 20+ other providers
- Google Postmaster Tools — free Google tool showing your domain reputation score directly from Google's perspective
How to Know When You Are Ready to Send Campaigns
You are ready to start cold email campaigns when all of these are true:
- ✅ Warmup has been running for at least 4 weeks
- ✅ Mail-Tester score is 8.5 or higher
- ✅ Google Postmaster shows domain reputation as "High" or "Medium"
- ✅ No blacklist hits on MXToolbox
- ✅ SPF, DKIM, and DMARC all passing
- ✅ Warmup open rates are consistently above 50%
Start small: Even when ready, begin your first campaign with 20-30 emails per day per account. Increase gradually over the first two weeks. A sudden spike from warmup volume to campaign volume can still trigger spam filters even on a warmed account.
NexusSender's built-in warmup system handles all of this automatically. Once you add your accounts and configure the ramp settings, the software manages the daily sending, opening, and replying — while you focus on building campaigns and closing deals.
Ready to get started? View NexusSender pricing or try the live demo to see the warmup system in action.