Email Domain Warmup: How to Build Sender Reputation from Scratch
By Email ExtractorPublished 7 min read
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Why Domain Warmup Matters
When you send email from a new domain, ISPs (Gmail, Outlook, Yahoo) have no history to judge your sending behaviour. A new domain has a neutral reputation, which means ISPs will scrutinise your early sends more carefully:
Sending stage
ISP treatment
What happens
Brand new domain (day 1)
Maximum scrutiny
Most emails land in spam or are throttled
Early warmup (weeks 1-2)
High scrutiny
ISPs watch engagement signals closely
Mid warmup (weeks 3-4)
Moderate scrutiny
Reputation building based on engagement
Established (weeks 5-8)
Normal scrutiny
Inbox placement based on accumulated reputation
Fully warmed (months 2+)
Standard treatment
Consistent inbox placement if metrics are healthy
What ISPs evaluate
Signal
Weight
What ISPs look for
Bounce rate
Very high
Hard bounces signal bad list quality; target under 2%
Spam complaint rate
Very high
Recipients marking as spam; target under 0.1%
Open rate
High
Low opens signal irrelevant or unwanted email
Reply rate
High
Replies signal legitimate communication
Unsubscribe rate
Medium
High unsubscribes signal unwanted email
Sending volume consistency
Medium
Sudden spikes suggest spam behaviour
Authentication (SPF, DKIM, DMARC)
High
Missing authentication raises flags
Content quality
Medium
Spammy content triggers filters
Link reputation
Medium
Links to blacklisted or suspicious domains
Domain age
Low-medium
Brand new domains are treated more cautiously
Pre-Warmup Setup
Domain and DNS configuration
Step
Action
Purpose
1. Register a new domain
Use a domain related to your brand (e.g. outreach.yourbrand.com or mail.yourbrand.com)
Separate cold email from your primary domain
2. Wait 2-4 weeks after registration
Let the domain age before sending
Very new domains are flagged more aggressively
3. Build a simple website on the domain
At least a landing page with company info and contact details
Domains with no website look suspicious
4. Set up SPF record
Add sending service IP(s) to DNS as SPF TXT record
Authorise your sending service
5. Set up DKIM signing
Generate DKIM keys; add public key to DNS
Prove email integrity
6. Set up DMARC policy
Start with p=none (monitoring); move to p=quarantine later
Email authentication policy
7. Set up MX records
Even if you do not receive email on this domain
Domains without MX records look suspicious
8. Verify DNS propagation
Use MXToolbox or Google Admin Toolbox to verify
Ensure records are correct and propagated
Sending infrastructure
Component
Recommendation
Notes
Email sending service
Dedicated IP or shared IP (for low volume)
Dedicated IP gives you full control of reputation
Mailbox provider
Google Workspace or Microsoft 365
For sending and receiving warmup replies
Number of mailboxes
3-5 mailboxes per domain
Distribute sending across mailboxes
Sending tool
Your cold email tool or warmup service
Must support throttling and scheduling
Tracking domain
Custom tracking domain on your sending domain
Avoid shared tracking domains
Unsubscribe link
Custom unsubscribe page on your domain
Required; also builds domain activity
Warmup Schedule
Manual warmup (sending to real contacts)
Week
Daily volume per mailbox
Total daily (5 mailboxes)
Content focus
Week 1
5-10
25-50
Personal emails to people who will reply
Week 2
10-20
50-100
Personal and semi-personal emails
Week 3
20-30
100-150
Mix of personal and light outreach
Week 4
30-40
150-200
Gradual introduction of cold outreach
Week 5
40-50
200-250
Increasing cold outreach percentage
Week 6
50-75
250-375
Mostly cold outreach at target volume
Week 7-8
75-100
375-500
Full target volume
Automated warmup (using warmup tools)
Warmup tool
How it works
Cost
Warmup Inbox
Sends and receives emails between real accounts; generates opens and replies
Tests inbox placement across ISPs; shows spam/inbox/tabs
$60-$150/month
Mail-Tester
Tests email score and deliverability factors
Free (limited)
MXToolbox
DNS and blacklist checking
Free basic; paid pro
Google Postmaster Tools
Gmail-specific delivery data
Free
Microsoft SNDS
Outlook/Hotmail-specific delivery data
Free
Blacklist monitoring
Check
How often
Tools
IP blacklist check
Daily during warmup
MXToolbox, MultiRBL
Domain blacklist check
Daily during warmup
MXToolbox, Google Safe Browsing
Spam trap hit check
After each send
Monitor bounce codes; watch for blacklist notifications
Common Warmup Mistakes
Mistake
Why it hurts
Correct approach
Sending too much too fast
ISPs flag sudden volume spikes
Follow a gradual warmup schedule
Sending only cold email (no warm email)
No positive engagement signals
Mix personal, transactional and warm email with cold
Skipping email authentication (SPF, DKIM, DMARC)
ISPs reject or flag unauthenticated email
Set up all authentication before sending
Using purchased lists during warmup
High bounce and complaint rates destroy new reputation
Send to verified, known contacts during warmup
Not monitoring metrics
Problems compound before you notice
Check metrics daily during warmup
Stopping warmup too early
Reputation is not yet established
Continue warmup for at least 4-6 weeks
Sending the same email to everyone
Looks like spam to ISPs
Personalise every email
No website on the sending domain
Suspicious to ISPs and recipients
Build at least a landing page
Using shared tracking domain
Inherits reputation of other users
Set up custom tracking domain
Ignoring Google Postmaster Tools
Missing Gmail-specific delivery data
Set up and monitor from day 1
Sending from one mailbox
All volume from one sender looks suspicious
Distribute across 3-5 mailboxes
Not having an unsubscribe option
Legal requirement; increases complaints
Include clear unsubscribe in every email
After Warmup: Maintaining Reputation
Practice
Frequency
Purpose
Monitor inbox placement
Weekly
Catch reputation drops early
Check blacklists
Weekly
Identify and address blacklisting quickly
Review bounce and complaint rates
After every send
Maintain clean sending metrics
Verify email lists before sending
Before every campaign
Prevent bounces that damage reputation
Remove unengaged recipients
Monthly
Keep list healthy; improve engagement rates
Continue some warm / personal email
Ongoing
Maintain positive engagement signals
Keep volume consistent
Ongoing
Avoid spikes that trigger ISP scrutiny
Update authentication records
When changing providers
Keep SPF, DKIM, DMARC current
Preparing Clean Lists for Warmup Sends
During warmup, list quality is even more critical than usual because every send shapes your domain reputation. Before sending to any list, upload your contact files to Email Extractor to extract and deduplicate email addresses, then verify them through a dedicated email verification service. Starting warmup with a clean, deduplicated, verified list prevents the bounces and complaints that can permanently damage a new domain's reputation.
