Building an IP warm-up schedule: daily volumes, who goes first and when to slow down
A warm-up schedule is a plan in which you grow the daily sending volume from a new IP address or domain step by step, usually over two to four weeks, starting with your most engaged recipients. The schedule itself is not sacred; the figures you measure along the way (bounces, refusals, complaints) decide whether you take the next step or hold still for a while.
Why a schedule and not just "take it easy"
Without a plan it goes wrong in two ways. Either someone ends up sending to the full list after all because the campaign happened to be ready, or people are so cautious that after three weeks no meaningful volume has been sent and no reputation has been built either. A schedule with daily volumes makes the agreement concrete for everyone involved in sending, and gives you a reference to measure deviations against.
An example schedule over three weeks
The schedule below is explicitly an example, meant for a sender who eventually wants to mail around 50,000 addresses per campaign. Whoever has smaller volumes scales the numbers down; the rhythm stays the same. The principle: roughly double per step, but with a slower start and a longer run-up at higher volumes.
- Days 1–2: 200 per day. Only addresses that opened or clicked in the past month.
- Days 3–4: 500 per day. Still the most active group.
- Days 5–7: 1,000 per day. Addresses active in the past three months are added.
- Days 8–10: 2,500 per day.
- Days 11–13: 5,000 per day. Addresses active in the past six months.
- Days 14–16: 10,000 per day.
- Days 17–19: 20,000 per day. Addresses active in the past year.
- Days 20–21: 35,000 to 50,000 per day. Full active list.
Note what is not in there: addresses that have done nothing for more than a year. You do not mail those during a warm-up. It is the period in which every recipient who ignores your mail counts double.
Spread the volume across providers
A common mistake is to send only to Gmail addresses on day one because they happened to be at the top of the list. Every large provider builds its own picture of you. Make sure each daily volume contains a mix of Gmail, Outlook, Belgian providers such as Proximus and Telenet, and business domains, roughly in the proportion of your real list. So sort your segments by engagement, not by domain.
Spread it across the day
A thousand messages within one minute looks different from a thousand messages over eight hours. A sending platform with rate limiting per domain handles that for you; if you send yourself, build in pauses. If you get temporary refusals with a text such as "try again later" or "too many connections", that is the recipient slowing you down. An automatic retry on greylisting and throttling absorbs that without you having to do anything.
When to slow down (and when to stop)
Every day, before you take the next step, look at three figures in your dashboard:
- Hard bounces. If they suddenly rise, an old segment slipped in that did not belong. Remove the bounces and repeat the daily volume instead of increasing.
- Refusals per recipient domain. If one provider suddenly refuses a large share, you have a reputation or authentication problem at that provider. Stay at the same volume until it is solved.
- Spam complaints. Every complaint during a warm-up weighs heavily. Several complaints on one day means: one step back in volume, and check whether the segment was really engaged.
The rule is simple: a step forward only if yesterday's figures were normal. A day standing still costs you nothing; doubling too early can cost weeks.
Warming up a domain without a dedicated IP
If you send through a shared IP pool, as with an SMTP relay with randomised IPs, those addresses already have a reputation. The warm-up is then about your domain: the receiving providers have no history yet of mail carrying your DKIM signature. That usually goes faster than warming up a bare IP address, but the principle remains: start with your best recipients and grow based on the figures. At 2Mail, IP warm-up with personal follow-up is included in the service, so the schedule is agreed and adjusted together with you.
Before day one
A warm-up only makes sense if the foundation is right. Check your SPF, DKIM and DMARC beforehand, make sure the reverse DNS of the sending IP matches the server name, and keep the sender name and sender address constant throughout the warm-up. Whoever changes sender halfway is effectively starting over.
Frequently asked questions
How long does a warm-up take?
Two to four weeks is common for most volumes. Large senders take longer. Faster is only possible if the figures allow it every day.
Can I send transactional mail at full strength right away?
Transactional mail is usually low in volume and high in engagement, which makes it an excellent start to a warm-up. Send it from day one, and let the campaigns follow the schedule.
What if I send nothing for a week?
A pause of a few days is no disaster, but weeks of silence let the reputation you built sink away. Then restart a few steps lower than where you left off.