IP Warmup

Gradually increase sending volume for new domains

IP Warmup

When you start sending from a new domain or IP address, mailbox providers like Gmail, Yahoo, and Outlook have no history to judge your reputation. Sending a large volume immediately can trigger spam filters and damage your deliverability. IP warmup is the process of gradually increasing your sending volume over days or weeks to build a positive sender reputation.

Why warmup matters

Mailbox providers assign a reputation score to every sending IP and domain. A new sender with no reputation is treated with suspicion. If you send 50,000 emails on day one from a brand-new domain, providers will likely throttle, defer, or reject a significant portion of those emails.

By starting with small volumes and increasing gradually, you demonstrate consistent sending behavior and give providers time to observe your engagement metrics (opens, clicks, low complaints). This builds trust and improves your inbox placement over time.

Warmup schedule

A typical warmup schedule spans 2-4 weeks. Here is a recommended progression:

Adjust this schedule based on your total list size. If your full volume is 5,000 emails, you can complete warmup in about a week. If your list is 500,000+, plan for 3-4 weeks.

Warmup best practices

Send to your most engaged contacts first

During warmup, prioritize contacts who have recently opened or clicked your emails (if you have prior engagement data from a different platform). High engagement signals tell mailbox providers that recipients want your email.

Maintain consistent sending

Send every day during the warmup period. Irregular sending patterns can reset the trust you have built. If you normally send three times per week, maintain that cadence but with increasing volumes.

Monitor your metrics closely

Watch for warning signs during warmup:

• Rising bounce rates — May indicate list quality issues. Pause and clean your list.
• Increasing deferrals — The receiving server is asking you to slow down. Reduce volume temporarily.
• Complaint spikes — Subscribers are marking your email as spam. Review your content and audience targeting.

Authenticate your domain

Before starting warmup, ensure your SPF, DKIM, and DMARC records are properly configured. Navigate to Organization Settings > Deliverability in Mailnaptic to verify your domain health badges are green.

Using warmup with Mailnaptic

Mailnaptic's warmupWorker manages sending volume progression automatically. When you add a new sending domain, the system tracks your daily volume and gradually increases the sending rate according to your warmup configuration.

You can monitor your warmup progress in the domain settings. The deliverability dashboard shows per-domain sending volumes and health indicators so you can track how warmup is progressing.

When to restart warmup

You may need to restart the warmup process if:

• You stop sending for more than 30 days.
• You switch to a new sending IP address.
• Your domain reputation has been severely damaged by complaints or blocklisting.

IP warmup requires patience, but it is one of the most important steps for long-term email deliverability success.