Definition
Email list temperature describes the level of active engagement from your subscriber base. A warm list has subscribers who regularly open, click, and convert. A cold list has subscribers who rarely or never engage. A hot list has subscribers who engage frequently and recently.
List temperature is a conceptual framework rather than a precise metric. It helps marketers think about the health of their list and make decisions about send frequency, re-engagement, and targeting.
List Temperature Levels
| Temperature | Engagement Level | Characteristics |
|---|---|---|
| Hot | Very high | Opened in last 7 days, clicked in last 30 days, recent purchase |
| Warm | Moderate | Opened in last 30 days, some clicks, engaged but not recently |
| Lukewarm | Low | Opened in last 90 days, few clicks, declining engagement |
| Cool | Minimal | No engagement in 90-180 days, at risk |
| Cold | None | No engagement in 180+ days, likely grey mail |
Why List Temperature Matters
Mailbox providers use engagement signals to determine inbox placement. Sending to cold list subscribers depresses your engagement metrics and signals to mailbox providers that your email is not valued. This can reduce inbox placement for your entire list, including your most engaged subscribers.
How to Warm a Cold List
- Segment by temperature: Separate hot, warm, and cold subscribers.
- Send to warm subscribers first: Focus engagement campaigns on your warmest segments to build positive signals.
- Re-engage lukewarm subscribers: Send a targeted win-back sequence to lukewarm subscribers who may still be reachable.
- Remove or suppress cold subscribers: Subscribers who have not engaged in 180+ days should be removed or suppressed.
- Warm new lists gradually: Imported or purchased lists should be warmed up slowly over 2-4 weeks.
Average Benchmarks
| Temperature | Percentage of List | Recommended Action |
|---|---|---|
| Hot | 10-20% | Full frequency, promotional content |
| Warm | 20-30% | Standard frequency, mix of content |
| Lukewarm | 15-25% | Reduced frequency, re-engagement |
| Cold | 30-50% | Win-back or suppress |
Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
Abandoned Cart Email
An abandoned cart email is an automated message sent to customers who added items to their online shopping cart but left without completing the purchase. It is one of the highest-converting email types in ecommerce.
AIDA Model for Email
The AIDA model (Attention, Interest, Desire, Action) is a classic copywriting framework used to structure email campaigns that guide subscribers from awareness to conversion.
AMP for Email
AMP for Email is a Google-developed framework that allows email messages to include interactive elements like forms, carousels, accordions, and live content. It turns static emails into dynamic, interactive experiences directly inside the inbox.
Anchoring Effect in Email Marketing
The anchoring effect is a cognitive bias where the first piece of information presented (the anchor) influences subsequent decisions, used in email to frame pricing and value perception.
Announcement Email
An announcement email is a dedicated campaign that communicates a specific update, milestone, or change to subscribers, from product launches and feature releases to company news and events.
Frequently Asked Questions
There is no single metric for list temperature. Use a combination of open rate (last 30 days), click rate, recency of engagement, and percentage of list that has engaged in the last 30, 60, and 90 days.
Partially. Some cold subscribers can be re-engaged through a targeted re-engagement campaign. Typically 5-15% of cold subscribers can be reactivated. The rest should be removed.
Sending to cold subscribers depresses your open and click rates, increases spam complaints, and signals to mailbox providers that your email is not wanted. This can reduce your overall deliverability.
Warming up a cold list takes 2-8 weeks depending on how cold the list is and how aggressively you pursue re-engagement. Gradual sending with re-engagement campaigns yields the best results.
Only for re-engagement purposes. Sending a win-back sequence to cold subscribers is acceptable. Sending regular promotional content to cold subscribers is damaging to your deliverability.