Email Warm-Up
The process of gradually increasing email send volume on a new IP address or domain to build trust with ISPs.
Email warm-up is the practice of slowly ramping up the number of emails sent from a new IP address or domain over a period of weeks. ISPs like Gmail, Microsoft, and Yahoo are suspicious of new senders that immediately blast large volumes, so a gradual increase signals legitimacy and builds a positive sender reputation.
A typical warm-up schedule starts with 50-100 emails per day and doubles every 2-3 days until you reach your target volume. During this period, you should send only to your most engaged subscribers — people who regularly open and click your emails — because high engagement rates during warm-up accelerate reputation building.
Best practices for warm-up:
- Start with your most engaged contacts first
- Maintain consistent sending patterns (same time of day, similar volumes)
- Monitor bounce rates and spam complaints closely during the ramp
- Use email verification to ensure your warm-up list is 100% clean — a single bounce spike during warm-up can set you back weeks
- Consider using a dedicated warm-up tool that automates sending and engagement patterns
Related Terms
Sender Reputation
A score assigned by ISPs to your email sending domain/IP that determines whether your emails reach the inbox.
IP Reputation
A trust score assigned by ISPs to a specific sending IP address based on its email sending history and behavior.
Bounce Rate
The percentage of emails that could not be delivered to the recipient's inbox.
Want to learn more?
Read our in-depth blog posts on email verification and deliverability.