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How to warm up your inboxes after migrating to Inframail

After migrating your domains to Inframail, you'll need to warm up your new inboxes to establish a strong sender reputation with email providers like Gmail and Outlook. This guide explains why warmup is necessary after migration, how long it takes, and strategies to start sending campaigns quickly.

Overview

You'll learn how to configure warmup settings during migration, upload inboxes to your sending platform, and gradually build your sending reputation to achieve great inbox placement rates for your cold email campaigns.

Prerequisites

  • Completed Inframail domain migration flow

  • CSV file exported from Inframail with warmup settings configured

  • Active account on a sending platform (Instantly, Smartlead, ReachInbox, Plusvibe, SalesHandy, Reply.io, or Woodpecker)

  • Updated nameservers and waited 24 hours for DNS propagation

  • SPF, DKIM, and DMARC records properly configured during migration

Compatibility

All Inframail plans: Warmup configuration is available during domain migration for Unlimited ($147/month) and Agency Pack ($387/month) subscribers.

Supported sending platforms: Instantly, Smartlead, ReachInbox, Plusvibe, SalesHandy, Reply.io, Woodpecker

Before you begin

Important: Skipping warmup or sending high volumes immediately after migration will damage your sender reputation and cause emails to land in spam folders. This can take weeks or months to repair.

Why warmup is necessary after migration: When you migrate domains to Inframail, your email inboxes are created on our infrastructure with no sending history. Email providers like Gmail and Outlook treat these as brand new senders and will closely monitor your initial sending patterns. Without warmup, bulk sending triggers spam filters.

Understanding warmup timelines

Warmup duration depends on your urgency and risk tolerance:

Scenario

Recommended Duration

Strategy

Standard warmup (recommended)

14 days

Full warmup only, no campaigns

Quick start (previously warmed domains)

7 days

Full warmup only, then start campaigns

Urgent campaigns (partial warmup)

Immediate start

80% warmup + 20% campaign emails

Pro tip: If your domains were already warmed before migration, you can reduce warmup to 7 days. However, new domains should always complete the full 14-day warmup for best results.

Step 1: Configure warmup settings during migration

During the Inframail domain migration flow, you'll reach the "Warmup Settings" step after creating your inboxes.

  1. Navigate to the Warmup Settings tab (13th step in the migration flow)

  2. Answer: "Would you like to turn on warmup automatically?"

    • Select Yes to embed warmup parameters in your CSV export

  3. Answer: "How many warm up emails do you want to start with?"

    • Select 10 (recommended for most users)

    • Choose 5 if you want a slower, more cautious ramp-up

    • Choose 15 if you're confident in your domain reputation

  4. Click Set to save your warmup configuration

What happens next: Your warmup settings are embedded into the CSV file with these parameters: Warmup Enabled (true), Warmup Limit (5/10/15), and Warmup Increment (1 email increase per day).

Step 2: Download and verify your CSV file

  1. Complete the remaining migration steps (email forwarders, redirects)

  2. On the File Exports step, select your sending platform from the dropdown

  3. Click Download to get your CSV file

  4. Open the CSV file and verify these columns are present:

    • Warmup Enabled - Should show true

    • Warmup Limit - Should show your selected starting number (5, 10, or 15)

    • Warmup Increment - Should show 1

Critical: Do not upload your CSV file to your sending platform until nameserver changes have fully propagated (minimum 24 hours after updating). Uploading too early will cause connection errors and failed warmup.

Step 3: Upload inboxes to your sending platform

After waiting 24 hours for DNS propagation:

  1. Log into your sending platform (Instantly, Smartlead, etc.)

  2. Navigate to the inbox import or bulk upload section

  3. Upload the CSV file exported from Inframail

  4. Verify that warmup is enabled for all imported inboxes

    • Instantly: Check for a green flame icon next to each inbox

    • Smartlead: Warmup must be manually enabled after import (recent platform update)

    • Other platforms: Confirm warmup status in inbox settings

Platform-specific note for Smartlead: Smartlead recently changed their import behavior and no longer automatically enables warmup from CSV files. After uploading, manually enable warmup for each inbox and set the starting point to match your Inframail configuration (5, 10, or 15).

Step 4: Monitor warmup progress

Your sending platform will automatically send and receive warmup emails to build reputation. Here's what to expect:

Standard 14-day warmup progression

If you selected a starting warmup limit of 10 emails per day:

  • Day 1: 10 warmup emails sent/received

  • Day 2: 11 warmup emails sent/received

  • Day 3: 12 warmup emails sent/received

  • Day 7: 16 warmup emails sent/received

  • Day 14: 23 warmup emails sent/received

  • Day 20+: Levels off at 20-30 warmup emails per day

Warmup score monitoring

Most sending platforms provide a warmup score (0-100) that indicates reputation health:

  • 90-100: Excellent - Ready to start sending campaigns

  • 70-89: Needs Work - Continue warmup for a few more days to watch for increases

  • Below 70: Poor - Contact Inframail support for assistance

Best practice: Don't start sending campaigns until your warmup score is consistently 90+ for at least 2-3 days. This ensures stable reputation before adding campaign volume.

Step 5: Start sending campaigns

Once your warmup period is complete, you can transition to sending cold email campaigns.

Option A: Full campaigns (after 14-day warmup)

If you completed the full 14-day warmup:

  1. Disable warmup in your sending platform (or leave it running at low volume)

  2. Start sending up to 40 campaign emails per inbox per day

    • Technical limit is 50 emails/day, but 40 is recommended for safe sending

  3. Monitor deliverability and spam placement for the first 3-5 days

  4. If performance drops, reduce volume by 25-30% until it stabilizes

Option B: Gradual ramp-up (safer approach)

For maximum deliverability:

  1. Start with 20 campaign emails per inbox per day

  2. Keep warmup running alongside campaigns for 2-3 weeks

  3. Increase campaign volume by 10-15 emails every 3-4 days if deliverability remains stable

  4. Monitor open rates and spam placement closely

  5. Pause scaling if you notice any performance drops

Partial warmup strategy (urgent campaigns)

If you need to start sending campaigns immediately after migration without completing the full warmup, use this approach:

80/20 warmup-to-campaign ratio

  1. Configure your sending platform to send 80% warmup emails and 20% campaign emails

  2. Example daily volumes per inbox:

    • 32 warmup emails

    • 8 campaign emails

    • Total: 40 emails per day

  3. Maintain this ratio for at least 7 days

  4. Gradually shift to 50/50 over the next week

  5. After 14 days total, transition to full campaigns or keep 20% warmup running permanently

Risk assessment: The 80/20 approach lets you start campaigns faster but carries higher risk of spam folder placement if your targeting or email content triggers filters. Only use this if you have urgent business needs and can't wait 14 days.

When to use 80/20: This strategy works best if your domains were previously warmed on another platform and you're simply migrating infrastructure. New domains should always complete full warmup first.

Safe sending limits and best practices

Daily sending limits per inbox

  • Maximum technical limit: 50 emails per inbox per day

  • Recommended safe limit: 40 emails per inbox per day

  • Conservative limit: 20-30 emails per inbox per day (for maximum deliverability)

Inboxes per domain

  • Recommended: 3-5 email addresses per domain

  • Maximum safe: 10 email addresses per domain

Pro tip: Spread your sending across multiple inboxes and domains rather than maxing out individual inboxes. For example, 100 emails/day across 5 inboxes (20 each) performs better than 40 emails/day from 2 inboxes.

Content best practices during warmup

To maximize deliverability during and after warmup:

  • Avoid links and images in first emails: Plain-text emails perform best during initial warmup

  • No spammy words: Avoid "free," "promotion," "limited time," excessive caps, or profanity

  • Personalize emails: Use recipient names, company names, and relevant context

  • Verify your lead list: Use tools like MillionVerifier or NeverBounce to avoid bounces

    • Keep bounce rate below 2% to maintain reputation

  • Use spin syntax: Vary email content to avoid pattern detection by spam filters

Troubleshooting warmup issues

Symptom

Likely Cause

Solution

Warmup not enabled after CSV upload

Platform didn't recognize warmup parameters or requires manual activation

Manually enable warmup in your sending platform. For Smartlead, click the warmup toggle for each inbox.

Warmup score stuck below 70

DNS records not properly configured or inboxes flagged by warmup pool

Verify SPF, DKIM, and DMARC records. Contact Inframail support to check infrastructure configuration.

"Sending account error" messages

Nameservers haven't propagated or credentials are incorrect

Wait 24-48 hours after nameserver update. Re-upload CSV if errors persist.

Platform disabled warmup automatically

Your inboxes negatively impacted the warmup pool (high bounce rate or spam reports)

Contact your sending platform support to re-enable. Review email content and list quality before resuming.

Low warmup scores after IP migration

Inframail moved you to a new IP due to blacklist or infrastructure issues

Re-upload inboxes to sync new settings. Run 1-week warmup on the new IP before sending campaigns.

Emails going to spam after warmup

Email content, targeting, or volume triggered spam filters

Reduce sending volume by 25-30%. Review content for spam triggers. Ensure you're targeting engaged recipients.

When to contact support: If warmup scores don't improve after 7 days, or if you see widespread "sending account error" messages across multiple inboxes, contact Inframail support immediately. These may indicate infrastructure issues that require backend fixes.

Monitoring inbox reputation (optional)

Inframail offers an optional Monitoring add-on ($12.41/month, billed annually) that provides:

  • Real-time IP and domain reputation tracking

  • Automatic blacklist monitoring and delisting (68.3% auto-delist success rate)

  • Deliverability alerts and health scores

To enable monitoring:

  1. Log into your Inframail dashboard

  2. Navigate to Monitoring in the left sidebar

  3. Click Subscribe to add monitoring to your account

  4. View IP and domain health scores in real-time

Free alternatives: If you don't subscribe to Inframail monitoring, you can use free tools like Google Postmaster Tools, Microsoft SNDS, or Sender Score to manually check your domain and IP reputation.

What to do if domains were blacklisted during previous use

If you're migrating domains that were previously blacklisted:

  1. Do not start warmup until Inframail requests delisting for the blacklisted domain

  2. Inframail will temporarily move your inboxes to a clean main domain during delisting

  3. Once delisting is confirmed, you can begin the standard 14-day warmup process

  4. Monitor warmup scores extra closely for the first week

Important: Attempting to warm up blacklisted domains without delisting will fail and may damage your other domains. Always wait for support confirmation before starting warmup on previously problematic domains.

After warmup: Ongoing maintenance

Even after completing warmup, maintain sender reputation by:

  • Keep warmup running permanently: Many users run 10-20 warmup emails per day indefinitely alongside campaigns

  • Monitor bounce rates: Stay below 2% bounces

  • Track spam complaint rates: Keep complaints below 0.1%

  • Maintain consistent sending: Avoid sudden volume spikes or long gaps in sending

  • Clean your list regularly: Remove unengaged contacts every 3-6 months

Pro tip: The recommended ongoing sending pattern is 80% warmup + 20% campaigns for the first 2-3 weeks after initial warmup, then 20% warmup + 80% campaigns permanently. This maintains reputation while maximizing campaign reach.

Limitations

  • Warmup settings are platform-dependent: Inframail can only embed warmup parameters in CSV files. Your sending platform must support and respect these settings.

  • No automatic warmup implementation: Inframail does not run warmup itself. You must use a third-party sending platform (Instantly, Smartlead, etc.) to execute warmup.

  • Settings not editable post-migration: Once you download your CSV file, warmup settings cannot be changed from the Inframail dashboard. You must edit CSV manually or restart the migration flow.

  • Warmup increment is fixed: The daily increase is always 1 email per day and cannot be customized during migration setup.

  • DNS propagation delays: Nameserver changes can take 24-72 hours. Inframail doesn't verify propagation status before allowing CSV download.

What's next

After completing warmup and starting campaigns:

Getting help

If you encounter issues during warmup:

  1. Collect diagnostic information:

    • Warmup scores from your sending platform

    • CSV file with warmup settings

    • Screenshots of any error messages

    • List of affected domains and inboxes

  2. Check DNS propagation: Use tools like WhatsMyDNS.net to verify nameservers have updated globally

  3. Contact Inframail support: Provide the diagnostic information above for fastest resolution

  4. Platform-specific issues: If warmup isn't enabling or scores are low, contact your sending platform support (Instantly, Smartlead, etc.) as they manage the warmup execution

Support hours: Inframail support is available 7am-12am PST. For urgent issues outside these hours, include detailed diagnostic information in your message for faster response when the team is online.

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