An Email Warm-Up Schedule for New Domains and New Inboxes

Warm up a new domain or inbox by sending a small daily volume to your most engaged recipients, then raising it about 50% at a time, never doubling, and holding each step for several days. Step back the moment you see deferrals, rate-limit errors or a rising spam rate. Two conservative schedules follow.

Before the tables, one honest point. No major mailbox provider publishes a warm-up schedule. Every schedule you find, including this one, is somebody's judgement. What providers do publish is the principle, and the schedule should follow from that.

What Google actually says about volume

Google's Email sender guidelines have a section titled "Increase sending volume slowly". The useful parts, quoted:

• "The more email that you send, the more slowly you should increase sending volume."
• "You can increase the sending volume more quickly when you send daily instead of weekly."
• "Start with a low sending volume to engaged users, and slowly increase the volume over time."
• "Avoid introducing sudden volume spikes if you do not have a history of sending large volumes. For example, immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops."
• "Send email at a consistent rate. Avoid sending email in bursts."
• "If messages start bouncing or start being deferred, reduce the sending volume until the SMTP error rate decreases. Then, increase slowly again."

It also explains why it applies to both domains and IPs: "DKIM and SPF quotas are specific to your domain," while "The IP address quota is shared for all senders that use that IP address." A new domain on a well-established ESP's shared IPs still has a domain to warm up.

From that, three rules shape everything below:

1. Never double. Each step is about 1.5 times the last, or less.
2. Hold each step for several sending days, so problems have time to show up before you add volume.
3. Best recipients first. Early volume goes to the people most likely to open and reply.

Schedule 1: a new cold-email inbox

For a new inbox on a new secondary domain (set up as in our secondary domain guide), heading for 40 sends a day. The 40 is an assumption about where you want to end up, not a safe number, and our post on cold emails per day per inbox covers how to choose yours.

Week	Sends per day (weekdays)	Who receives them
1	5	Colleagues, friends, existing contacts who will reply
2	8, then 12	Existing contacts plus your best-fit, verified prospects
3	18	Verified prospects
4	27	Verified prospects
5	40	Verified prospects; hold here

Each step is roughly 1.5 times the one before. If your platform's automatic warm-up is on, its sends count towards the total. The schedule is about how much mail leaves the inbox, not just how much goes to prospects.

Schedule 2: a new marketing domain

For a newsletter or marketing programme moving to a new sending domain, with a target of 20,000 messages a day. Start with your most recently engaged subscribers, for example people who opened or clicked in the last 30 days, and add older segments as volume grows.

Days	Sends per day	Audience
1-3	500	Engaged in last 30 days
4-6	750	Engaged in last 30 days
7-9	1,100	Engaged in last 30 days
10-12	1,700	Engaged in last 60 days
13-15	2,500	Engaged in last 60 days
16-18	3,800	Engaged in last 90 days
19-21	5,700	Engaged in last 90 days
22-24	8,500	Engaged in last 6 months
25-27	12,800	Engaged in last 6 months
28-30	19,000	Full active list
31+	20,000	Full active list

That is about a month at a steady 1.5x every three days. Two things will slow it down in practice, and should:

• You run out of engaged people. If your 30-day engaged segment is 800 people, you can't send 1,100 to it. Stay at its size longer rather than padding with cold segments.
• You send weekly, not daily. Google says daily senders can increase faster. If you send twice a week, treat each send as a step and expect the ramp to take roughly twice as long.

Total volume passes 5,000 a day around day 19. Google's line is close to 5,000 a day to personal Gmail accounts, so depending on how much of your list is on Gmail you'll cross it then or soon after, and once you do, Google classifies the domain as a bulk sender permanently. Make sure everything in Gmail and Yahoo's bulk sender requirements is in place before you get there, not after.

Stop rules: when to slow down

A schedule without stop rules is just a calendar. Check these before each increase:

Signal	Where you see it	What to do
Gmail 4.7.28 responses	Your ESP's bounce/deferral log	Google: stop for at least 10 minutes, resume on one connection, add connections one at a time. Drop to the previous step for 3+ days
Other 421 or 451 deferrals rising	Bounce/deferral log	Hold volume; don't increase until they fall back
Hard bounces above about 2%	ESP reports	Stop. The list needs cleaning, not more warm-up
Spam rate above 0.1%	Google Postmaster Tools	Hold or step back; tighten the audience to more engaged segments
Opens or replies falling while volume rises	Your own reporting	Possible spam placement. Hold and check a few seed inboxes

Google's advice on rate limiting is specific. When it rejects with 4.7.28 and doesn't say whether the DKIM, SPF or IP quota was exceeded, "assume that all three are affected."

The bounce line deserves emphasis because warm-up is where most avoidable damage happens. A new domain has no history to dilute a bad send. If the first few hundred messages include a few dozen dead addresses, the domain's first record is a bounce problem. Verify every list before it touches a domain in warm-up. Our free email checker handles single addresses, and catch-all and risky results are better held back until the domain is established.

About automated warm-up tools

Many cold email platforms include a warm-up feature. Typically, inboxes in a shared network send to each other, open, reply, and move messages out of spam. Instantly's setup guide, for example, says to warm up new accounts "for at least 2 weeks" before campaigns.

What we can say with confidence:

• They do create consistent daily sending history, which Google's guidance favours over bursts.
• The engagement comes from other warm-up inboxes, not your prospects.
• None of Google, Yahoo or Microsoft has published how it treats warm-up network traffic, so any claim about exactly what it achieves is a vendor's claim.

So use them, if you like, as a floor of steady activity, and don't let a "100% warm-up health" score stand in for the stop rules above. Real recipients replying to real mail are what you're trying to build.

When to warm up again

• New domain or subdomain: always.
• New dedicated IP: yes. IP reputation starts from nothing. See shared vs dedicated IP.
• Moving ESP on the same domain and shared IPs: the domain has history, but Google's guidance says "After making any significant changes to your sending infrastructure or email header structure, increase the modified segment of traffic separately." A shorter ramp is sensible.
• A domain that has been idle for months: treat it as partly cold and ramp up again.
• Changing the format of your mail substantially: Google says to "gradually increase the sending volume of messages with the new format."

The practical takeaway

Pick a target volume, start at a tenth of it or less to your best recipients, and step up by about half each time, holding each step for a few days. Check the stop rules before every increase and step back without arguing with them. And clean the list first: no schedule survives a bad first send.