IP warmup
What is IP warmup?
IP warmup is the practice of gradually ramping up email send volume from a new sending IP address or domain — starting with a small daily cap to engaged recipients and increasing it over a period of days or weeks — instead of sending at full volume immediately. Mailbox providers have no sending history to judge a brand-new IP or domain by, so a sudden high-volume burst reads as spam-like behavior and gets throttled or blocked; a gradual ramp lets sender reputation build alongside volume.
More detail
A warmup schedule is typically expressed as a daily send-volume cap that increases on a set curve (for example, doubling every few days) until it reaches the sender's target daily volume — sending above that day's cap risks throttling or blocklisting on an IP or domain still building reputation.
Warmup applies to both dedicated IPs and new sending domains; a platform that provisions a dedicated IP for a customer above a volume threshold typically enforces the ramp automatically, deferring or rejecting a batch that would exceed the current day's cap rather than letting it damage reputation.
Frequently asked
- Why can't a new sending IP just send at full volume from day one?
- Mailbox providers have no history to judge a brand-new IP by, so a sudden high-volume burst looks like spam behavior and gets throttled, blocklisted, or routed to spam — a gradual ramp lets the IP build a positive sending reputation as volume increases.
- How long does an IP warmup schedule typically take?
- It varies by target volume, but a warmup ramp commonly spans one to several weeks, starting at a small daily cap and increasing on a set curve until it reaches the sender's full target daily volume without triggering spam filters along the way.
See also
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