Warming up a new sending domain and IP

Warming up a new sending domain and IP means sending a small, steadily increasing volume of legitimate email over several weeks so that mailbox providers like Gmail, Outlook, and Yahoo learn that your IP and domain are trustworthy. A brand new IP has no reputation, and a sudden burst of mail from it looks exactly like a spam run, so a gradual ramp is the single most important step for good deliverability.

Why warming up matters

Inbox providers score senders on volume patterns, complaint rates, and authentication history. A cold IP that suddenly sends thousands of messages triggers rate limiting, temporary deferrals (4xx errors), or outright blocking. By starting small and growing predictably, you build a positive reputation on both the IP and the From: domain before you rely on them for important mail.

Set up authentication first

Never start a warmup without correct authentication. Warming an IP while messages fail alignment simply teaches providers to distrust you. Before your first send, publish these DNS records for the sending domain:

1. SPF: authorize the sending host, for example v=spf1 include:_spf.yourhost.com -all.
2. DKIM: publish the public key your server generates as a TXT record at selector._domainkey.yourdomain.com so outgoing mail is cryptographically signed.
3. DMARC: start in monitoring mode with v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com, then tighten to quarantine or reject once reports look clean.
4. Confirm valid forward and reverse DNS (PTR) for the sending IP. On a dedicated IP this is straightforward; if you need help setting it, reach out through our support team.

A sample warmup ramp

There is no single official schedule, but the shape is always the same: start with tens of messages per day and roughly double every few days, watching engagement before you increase. A typical four week ramp toward a few thousand daily messages looks like this.

Practical rules during the ramp

• Send to your most engaged recipients first. Opens, replies, and low complaints are the signals that build reputation fastest.
• Keep volume growth to roughly double per step, and hold steady if you see rising bounces or deferrals.
• Clean your list before you begin. Sending to stale or invalid addresses raises bounce rates and damages a fresh IP quickly.
• Warm each mailbox provider in parallel; Gmail, Outlook, and Yahoo maintain separate reputations.
• Watch deferrals as feedback, not failure. A 4xx response usually means slow down, so pause increases for a day or two.

Monitor and adjust

Track delivery, bounce, and complaint rates throughout, and read the aggregate DMARC reports arriving at your rua address. If a provider throttles you, hold volume flat until deferrals clear rather than pushing harder. A dedicated Class C IP helps here because your reputation is not shared with unknown neighbors, so the sending history you build stays entirely your own. Consistency after the ramp matters too, since long idle gaps let reputation decay.

For more on the authentication records behind deliverability, see our email and deliverability guides, and review the DMARC specification at RFC 7489.