List warming gradually builds an email senders reputation, essential for new domains or inactive lists.
List Warming Overview
List warming helps you gradually increase email volume to build a positive sender reputation.
Use it when:
- Starting with a new domain or IP
- Switching ESPs
- Re-engaging an inactive list
Note:
List warming is not guaranteed and requires time, consistency, and monitoring.
Preparation Before Warming
Engagement
- Start with your most engaged contacts
- Prioritize users active in the last 30–60 days
- Increase volume gradually (avoid spikes)
Content
- Use proven, high-performing content
- Avoid overly niche messaging unless segmented
- Ensure emails render correctly (e.g., test with Litmus)
Hygiene
- Clean your list before sending
- Remove:
- Invalid emails
- Inactive users
- Avoid spam traps (critical risk)
Permission
- Only send to opt-in contacts
- Match expectations:
- Frequency
- Content relevance
- Avoid misleading subject lines or offers
Building Sender Reputation
Positive Signals
- Opens
- Clicks
- Clean list (good hygiene)
- Proper authentication (SPF, DKIM, DMARC)
Negative Signals
- Spam traps
- Sudden volume spikes
- Spam complaints
- Hard bounces (invalid emails)
- Blacklistings (IP/domain)
- Risky content (e.g., crypto, gambling, dating)
Key Warming Expectations
- Some spam placement and soft bounces are normal
- Consistency improves placement over time
- Pause and reassess if:
- High rejection rates
- Low engagement
Technical Setup (DNS)
SPF
- Defines authorized sending IPs for your domain
DKIM
- Adds a digital signature to verify sender authenticity
DMARC
- Aligns SPF + DKIM
- Lets you:
- Monitor activity
- Set policies (e.g.,
p=reject for stricter protection)
Additional Best Practice
- Use branded tracking domains for links to improve trust and deliverability
