Email domain warm up and IP warmup, step by step

What an email domain warm up or IP warmup is#

Warming up is sending from a new sending domain or a new IP address at low volume first and raising it gradually, so mailbox providers see a steady pattern of wanted mail before they see your full volume. M3AAWG, the industry’s anti-abuse working group, describes domain warming as “a practice used to introduce a new domain to MBPs so they may sufficiently evaluate your messages for acceptance and placement”, which “involves gradually increasing the volume of emails sent from the new domain over time.”^[1]

The same idea applies to an address. IP warming is the term for a new dedicated IP, and Gmail’s own troubleshooting page uses “warming up the sending domain or IP address” for the act of backing off and resuming slowly when it rate-limits you.^[2] Either way, the goal is the same: let a reputation form on mail people want, before the volume is large enough to look like a spam run.

Why a new domain or IP needs warming#

Mailbox providers decide what to do with a message partly by the history of whoever sent it. A new domain or address has no history, and the providers say plainly what that means:

• M3AAWG: the reputation of a newly registered domain “usually starts as unknown, which makes it similar to bad in that it does not yet have any sending history”. An established domain that has never sent mail and suddenly sends a lot “can also be problematic”.^[1]
• Microsoft: “IPs not previously used to send email typically don’t have any reputation built up in our systems. As a result, emails from new IPs are more likely to experience deliverability issues.”^[3]
• Yahoo: one of its rejection reasons for “excessive unsolicited messages” reads: “You may have setup the IP you are using to send email very recently and did not increase the email traffic slowly.”^[4]
• Gmail: “Gmail tracks volume, feedback, and limits per domain and IP address”, and “immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops.”^[5]

Domain warm up vs IP warmup: what is different#

Providers keep reputation for both the domain in your authentication and the address the mail leaves from. Gmail says its DKIM and SPF quotas are specific to your domain, while an IP address quota “is shared for all senders that use that IP address”.^[5] Which of the two you have to warm depends on what is new.

Two consequences are easy to miss. First, moving to a new provider’s shared pool does not reset your domain: if the domain already has a history of wanted mail, it keeps it. Microsoft notes that new IPs added under an existing SPF record “typically experience the added benefit of inheriting some of the domain’s sending reputation”.^[3] Second, a new subdomain is a new name. M3AAWG advises that “when sending from a new subdomain, to be safe, domain warming is recommended even if the organizational level domain already has an established reputation.”^[1]

Do you need a dedicated IP at all?#

Usually not until volume is high and steady. M3AAWG’s guidance is that “consistency of volume, whether high or low, plays an integral part in the determination of IP reputation”, and that a shared pool combines several senders’ mail “to sustain consistent overall average sending volume”.^[1] A small or bursty sender on an address of its own gives providers too little to judge. The trade-offs are set out in shared IP pool and dedicated IP.

How long does a warm-up take?#

There is no single answer, and anyone who gives one without asking about your volume is guessing. The published guidance, side by side:

Microsoft’s estimate for a new IP at Outlook.com is shorter: “A new IP can expect to be fully ramped within a couple of weeks or sooner depending on volume, list accuracy and as long as their junk email complaint rates are kept at a minimum.”^[3] Google gives no duration at all. It names the three things that set the pace instead:^[5]

1. How much you send. “The more email that you send, the more slowly you should increase sending volume.”
2. How often you send. “You can increase the sending volume more quickly when you send daily instead of weekly.”
3. How recipients react. Send only to people who subscribed, and give them a way to unsubscribe.

Before you send the first message#

A warm-up builds a reputation on whatever you send. If authentication fails or the list is stale, you are building the wrong one. Get these right first:

The authentication and DNS items are Gmail’s published requirements,^[5] and the mechanics are in DKIM, SPF and DMARC explained. Postmaster Tools data only appears once the domain is verified and shows mail to personal Gmail accounts only.^[6] Microsoft reminds senders with new IPs to add them to their Junk Email Reporting Program account,^[3] and SNDS gives the owner of an IP range daily data such as mail volume and complaint rates for each address.^[7]

An example warm-up schedule#

The example assumes a sender whose eventual volume is 50,000 messages a day, mailing on most days. Each week has two steps; hold each step for two to four days, and move up only if the previous step’s deferrals, bounces and complaints stayed flat.

Three rules matter more than the numbers. Spread each day’s mail across the day rather than sending the batch at once — M3AAWG says so directly, and Gmail asks senders to “send email at a consistent rate” and avoid bursts.^[1][5] Keep mailing on a regular rhythm until the domain is warm, because M3AAWG notes it is “preferable to send campaigns on a regular basis until the domain is sufficiently warmed up.”^[1] And if you change the template or the infrastructure mid-way, Gmail asks you to ramp the changed segment separately.^[5]

Transactional mail — receipts, password resets — cannot wait for a ramp. If the new domain carries both, let transactional mail flow at its natural rate (it is small, and people expect it) and hold the ramp on marketing. Better still, send them from separate subdomains, which is what M3AAWG recommends anyway (“offers.mybrand.com for marketing, info.mybrand.com for transactional”).^[1] The difference between the two is in transactional vs marketing email.

Step by step: how to warm up a new domain or IP#

The procedure, in order. The first two steps happen before any volume; the rest repeat until you reach full volume.

1. 1

   Authenticate and set up monitoring

   Publish SPF, DKIM and DMARC for the new domain, make sure the sending IP has a PTR record that resolves back to it, and verify the domain in Google Postmaster Tools. If you own the IPs, register them in Microsoft SNDS and its Junk Email Reporting Program.

2. 2

   Clean and segment the list

   Suppress past bounces and complaints, and split your consented list by recent engagement: opened or clicked in the last 30 days, in the last 90 days, and older. Never warm up on bought, scraped or appended addresses.

3. 3

   Start small, with your most engaged recipients

   Send a small share of your eventual daily volume to the 30-day segment, spread across the day at a steady rate rather than in one batch.

4. 4

   Raise volume in modest steps

   Every few days, raise the daily volume by about half, never a sudden doubling, and widen the audience to older engaged segments. Keep sending on a regular rhythm until you reach full volume.

5. 5

   Watch the signals at every step

   Check deferrals and bounces in your SMTP responses, the spam rate and delivery errors in Postmaster Tools, and opens and clicks per mailbox provider. Keep the Gmail spam rate below 0.1%.

6. 6

   Hold or step back when a signal rises

   If deferrals, bounces or complaints rise, reduce volume until they fall, then increase slowly again. After a Gmail 4.7.28 error, pause for at least 10 minutes and resume on a single connection.

What to watch during a warm-up, and when to slow down#

A warm-up is a feedback loop: you raise volume, providers answer, you adjust. The signals come from three places — the SMTP responses to your own sends, the providers’ dashboards, and how recipients behave.

Deferrals and rate limits#

Google’s instruction is specific: “If messages start bouncing or start being deferred, reduce the sending volume until the SMTP error rate decreases. Then, increase slowly again.” For a 4.7.28 rate-limit error it asks senders not to send for at least 10 minutes, then resume from a single connection and add connections one at a time.^[5] A temporary failure is a request to slow down, not a bounce: retry it with growing delays, as the difference between the two in hard bounce vs soft bounce explains.

Complaints#

Yahoo sets its line at 0.3% and asks bulk senders to use its Complaint Feedback Loop to track it.^[9] During a warm-up the audience is your most engaged readers, so complaints should be at their lowest; a rise at this stage is a clear sign to stop and look at who you added. See complaint rate for how the number is calculated.

Opens and clicks#

M3AAWG lists opens and clicks as warm-up signals with two readings: a sudden drop “may indicate your mail is going to the junk folder”, and large spikes “may indicate security appliances giving your mail extra scrutiny.”^[1] Watch them per mailbox provider, not only in total — a problem at one provider is diluted by the others in a combined number.

Warming up a domain or IP on Rasket#

On Rasket, most senders warm a domain, not an address. Mail goes out over a shared pool that is already sending, so there is no IP to warm; what is new is your verified domain, which signs your mail with its own DKIM key. We recommend sending from a subdomain such as mail.example.com, so its reputation stays apart from the rest of your organisation’s mail — and, following M3AAWG, warming that subdomain even when the parent domain has a good history.^[1]

• Ramp with segments. Campaigns (our marketing feature) send to a segment you define and can be scheduled, so a warm-up is a series of campaigns to your most engaged segment first, widened step by step.
• Watch the rates. The Metrics page shows deliverability, bounce, complaint, open and click rates by period and by domain, and every message produces delivery events you can receive as webhooks.
• Keep the list clean automatically. A permanent bounce or a spam complaint puts the address on your team’s suppression list, so later sends skip it — see how a suppression list works.

A dedicated IP is an add-on from the Scale plan, recommended for teams sending 5,000 or more emails a day. The address is set up as soon as you buy it and warms up over about six weeks on its own schedule while your mail keeps flowing: while it warms, the share of your mail it carries grows and the rest continues over the shared pool, so you do not hold back sends or run a ramp of your own for the address. Your plan settings show how far the warm-up has got. A new domain on a dedicated IP still benefits from the domain ramp above.

Warm-up myths#

• Documented by Google “My list is clean, so I can skip it.” Gmail asks senders without a history of large volumes to avoid sudden spikes, whatever the list’s quality.^[5]
• Documented by Google “There is one standard schedule every provider uses.” Google gives no schedule; it says the pace depends on how much you send, how often, and how recipients react.^[5]
• Unproven “A warm-up service that trades opens between inboxes will warm me up.” M3AAWG says “artificial warming practices are not recommended and may be illegal.” A reputation built on fake engagement describes mail nobody wants.^[1]
• Unproven “A new subdomain inherits the parent’s reputation.” Some of it may, but M3AAWG recommends warming a new subdomain anyway.^[1]
• Documented by Google “Once warm, always warm.” Reputation follows behaviour. Gmail asks senders to keep a consistent rate and warns that high spam rates lead to more spam classification over time.^[5]
• Unproven “A dedicated IP always delivers better.” It isolates your reputation, good or bad. At low or irregular volume, a shared pool’s steady traffic is what M3AAWG credits with sustaining a reputation.^[1]

Once you are sending at full volume, keep watching the same numbers. Our guide to Google Postmaster Tools explains each dashboard, the deliverability guide covers the wider picture, and getting out of the Gmail Promotions tab covers where mail lands once it is delivered.