Email Domain Warm-Up Guide

Important Notice for New Customers

If you plan to send large email campaigns within your first 3 weeks as a new customer, you have three options:

1. MailGro (e.g., newsletter@mailgro.com) - Ready to send immediately with no warm-up required
2. PatchSend subdomain (e.g., newsletter@mybrand.patchsend.com) - Requires domain warming (detailed below)
3. Your own custom domain (e.g., newsletter@mydomain.com) - Requires domain warming (detailed below)

When you add a new Email Sending Domain via Settings > Email Settings, domains without established reputation need time for mailbox providers like Gmail and Outlook to get familiar with them—and that means you need to warm them up.

Warming up your domain is the process of gradually increasing your email volume while targeting your most engaged contacts first. This helps build a positive sender reputation, improves inbox placement, and protects your deliverability long-term.

This guide outlines our recommended warm-up approach for PatchSend subdomains and custom domains, best practices, red flags to watch for, and expert recommendations to help you establish reliable deliverability.

Why You Need to Warm Up a New Email Domain

When sending from a new domain or IP, email providers like Gmail, Outlook, and Yahoo have no prior history to evaluate your trustworthiness. Without a warm-up process, your emails are more likely to be flagged as spam or rejected.

Warming up your domain gradually helps you:

• Build credibility with mailbox providers
• Improve inbox placement
• Avoid bouncebacks and complaint-based throttling
• Create a foundation for successful long-term campaigns

Domain Warming Requirements

Domain warming is required for:

• PatchSend subdomains (e.g., updates@mybrand.patchsend.com)
• Custom domains that you own (e.g., marketing@yourbrand.com)

No warming needed for:

• MailGro (e.g., promo@mailgro.com) - This option is pre-warmed and ready for immediate high-volume sending

Recommended Warming Approach (PatchSend & Custom Domains)

Start with Low Volume

• Send very small batches at first (50–100 emails/day)
• Double (or at most, increase 1.5x) the daily volume every 2–3 days if engagement stays strong (opens/clicks above 20–30%, spam complaints at 0%)
• Full warmup usually takes 4–6 weeks, depending on your eventual sending volume

Target Engaged Recipients First

• Begin with your most active and engaged audience (people who have opened or clicked in the last 30–60 days)
• Don't start with cold lists—providers need to see signals that recipients want your emails

Content & Consistency

• Send real, valuable content—not just test messages. ISPs recognize engagement signals
• Keep content simple at first (plain text or light HTML)
• Maintain consistent sending times (e.g., weekday mornings)

Gradually Introduce Campaigns

• Once you've built up trust (after ~2–3 weeks), you can start introducing larger sends and colder segments, but do it slowly
• Important: Only increase your email volume if metrics remain healthy. If you see signs of deliverability issues, pause or reduce volume by 25 to 30 percent until performance normalizes.

Considerations Based on List Size

For Accounts with Fewer Than 20,000 Contacts

You may complete the warm-up in three weeks or less if your engagement metrics remain strong throughout.

• Focus more on segmentation by engagement than by sheer list size. Start with your top 1,000 most engaged recipients and build from there
• Avoid the temptation to rush. Even if the total list is small, reputation damage can still occur from high bounce or complaint rates
• Prioritize list hygiene and clear opt-in records before beginning

For Larger Databases (20,000 or More Contacts)

Expect a full 30 to 45 days to reach full sending volume.

• Segment more granularly by engagement window: start with 7-day openers, then 14, 30, 60, and 90
• Consider running warm-up across multiple subdomains or IP addresses if available
• Establish warm-up goals by provider (e.g., 3,000 to Gmail, 1,000 to Outlook) rather than by overall list count
• Important: Only increase your email volume if metrics remain healthy. If you see signs of deliverability issues, pause or reduce volume by 25 to 30 percent until performance normalizes.

In both cases, quality and engagement always matter more than quantity. A small list with high engagement will warm up faster and more safely than a large list that includes cold or unverified contacts.

30-Day Warm-Up Schedule

Week 1: Establishing Your Foundation

Day 1 to 2

• Send 50 to 100 emails per provider (Gmail, Yahoo, Outlook)
• Target only your most engaged contacts (recent openers or clickers)
• Keep content simple and valuable with a clear call to action
• Monitor open rates, click rates, bounce rates, and spam flags

Day 3 to 4

• If open rate is above 20 percent and bounce rate is below 2 percent, increase to 200 emails per provider
• Continue targeting only highly engaged recipients
• Slightly vary email templates while maintaining consistent branding
• Use inbox placement tools to check for spam issues

Day 5 to 7

• Increase to 400 emails per provider if performance remains strong
• Begin introducing moderately engaged contacts (opened within 60 days)
• Establish a consistent sending schedule (time of day and frequency)
• Remove any bounced or invalid addresses immediately

Week 2: Controlled Growth

Day 8 to 10

• Increase to 600 to 800 emails per provider
• Include subscribers who engaged within the last 90 days
• Introduce different types of content to keep engagement high
• Begin monitoring sender reputation using tools like Google Postmaster

Day 11 to 14

• If metrics remain stable, increase to 1,000 to 1,500 emails per provider
• Increase volume by no more than 30 to 50 percent daily
• Start including subscribers with engagement within 120 days
• Monitor spam complaints, which should remain below 0.1 percent

Week 3: Scaling Up

Day 15 to 17

• Increase to 2,000 to 3,000 emails per provider
• If deliverability declines, reduce volume by 25 to 30 percent
• Expand to slightly older segments of your list
• Match sending times and frequency to your long-term plan

Day 18 to 21

• Increase to 4,000 to 5,000 emails per provider
• Add more content types while maintaining relevance and value
• Begin sending re-engagement emails to less active contacts
• Monitor DMARC reports to ensure authentication is correctly configured

Week 4: Reaching Full Volume

Day 22 to 25

• Increase to 7,500 to 10,000 emails per provider
• If higher volumes are required, grow slowly at 20 to 30 percent daily
• Begin sending a full mix of content types (promotional, educational, etc.)
• Keep verifying engagement metrics before each increase

Day 26 to 30

• Reach your full intended sending volume
• Begin executing your complete email marketing strategy
• Maintain consistency in timing and volume
• Monitor key deliverability metrics continuously

Post Warm-Up: Ongoing Best Practices

After warming up your domain, continue with these steps to preserve your reputation:

• Maintain consistent sending patterns
• Monitor engagement and bounce rates weekly
• Use list cleaning tools to regularly remove invalid or unengaged contacts
• Send only to confirmed opt-in subscribers
• Use double opt-in for new signups

Deliverability Pro Tips

Set up authentication before sending

• Ensure SPF, DKIM, and DMARC are configured
• Match WHOIS records to your website contact info for added trust

Segment by engagement

• Start with your most engaged recipients
• Gradually add contacts who opened within the last 30, 60, 90, then 120 days

Use two subdomains

• One for promotional messages
• One for transactional or system alerts

Use consistent branding

• Keep logos, sender names, and messaging aligned with your existing digital presence
• If mailbox providers associate the domain with your known brand, they are more likely to trust it

Red Flags to Avoid

Watch out for these warning signs that indicate you need to slow down or pause your warm-up:

• Bounce rate above 3 percent
• Open rate below 10 percent
• Spam complaint rate above 0.1 percent
• Delivery deferrals or throttling
• Blocklist-related bounces
• Authentication failures

Recommended Tools

• List Cleaning: ZeroBounce, NeverBounce, Emailable
• Inbox Testing: Mail-Tester, GlockApps
• Reputation Monitoring: Google Postmaster Tools, Talos Intelligence
• Email Warm-Up Platforms: Mailwarm, Lemwarm, Instantly

No One-Size-Fits-All Schedule

Each domain warm-up process will vary based on your list quality, past engagement, and email strategy. Most senders will reach full volume in three to six weeks.

Important: Only increase your email volume if metrics remain healthy. If you see signs of deliverability issues, pause or reduce volume by 25 to 30 percent until performance normalizes.