IP Warming
IP warming is the process of gradually increasing the volume of emails sent from a new IP address to build a positive sender reputation with email providers.
What Is IP Warming?
When you start sending from a new IP address, email providers have no history to judge your sending behaviour. If you immediately blast thousands of emails, ISPs will flag the activity as suspicious — it looks like spam. IP warming involves starting with a small volume (perhaps 50-100 emails per day) and gradually increasing over 2-6 weeks. During this period, you should send to your most engaged subscribers first, as their opens and clicks signal to ISPs that your emails are wanted. The warming schedule depends on your target volume — warming to 10,000 emails per day typically takes 3-4 weeks.
Why It Matters for Newsletters
Skipping IP warming is one of the most common mistakes newsletter creators make when switching platforms. Sending at full volume from a cold IP almost always results in deliverability problems — emails landing in spam, being rate-limited, or getting blocked entirely. The damage can take weeks to recover from.
Best Practices
- Start with your most engaged subscribers during the warming period
- Increase volume by no more than 50-100% per day
- Monitor bounce rates and spam complaints closely during warming
- Pause and investigate if bounce rates exceed 3% during warming
- Plan for 2-4 weeks of warming before sending at full volume
How Aldus Handles This
Aldus sends through Resend's managed infrastructure, which is already warmed and maintains a strong sender reputation. This means you don't need to worry about IP warming — you can start sending immediately.