Email Warm-Up
How to warm up a new mailbox for cold email without getting blocked: emails per day, week by week, and which metrics to watch. + A ready-made 28-day schedule.
Email warm-up is the gradual increase in the number of emails sent from a new mailbox or domain so that mailbox providers can build a positive sender history. Without warm-up, Gmail, Yandex and Mail.ru see a sudden spike from an unknown address and send the mail to spam. The minimum is 7 days; for cold outreach, 3–4 weeks.
At the end of this article you'll find a ready-made 28-day warm-up schedule with daily volumes and the stop signals that tell you to pause. Copy it and adapt it to your volume.
At a glance: warm-up in numbers
| Parameter | Benchmark | Source |
|---|---|---|
| Minimum warm-up period | 7 days | Holymailer |
| Time before full-scale cold outreach | 3–4 weeks | Industry practice |
| Starting volume on a new mailbox | 5–10 emails a day | Industry practice |
| Working volume of cold emails per mailbox | 30–50 a day | Industry practice |
| Gmail spam complaint threshold | below 0.3%, target below 0.1% | Google, 2024 |
| Mail.ru complaint threshold at up to 10,000 emails a month | 1.1% | Mail.ru |
| Google Workspace sending limit | 2,000 emails a day per user | Google Workspace |
Why warm up a mailbox if SPF and DKIM are already set up
SPF and DKIM prove that an email really comes from you. Warm-up proves that you can be trusted. These are two different things.
Mailbox providers judge senders by their history: how many emails they've sent, whether people opened them, replied, or complained. A new mailbox has no history. If it sends 300 emails to strangers on day one, the filter sees a classic spammer pattern: a new address, a sudden spike, no replies.
Warm-up does one job: it builds a history of normal correspondence before cold outreach begins. Setting up SPF and DKIM is a prerequisite, not a substitute for warm-up.
How long does email warm-up take
At least 7 days, ideally 3–4 weeks. Holymailer builds in at least 7 days of gradual warm-up with limits that rise smoothly. For cold outreach it's better to stretch the process to a month: cold emails get fewer replies than normal correspondence, so your reputation needs a buffer.
The timeline depends on three factors:
- Domain age. A domain registered yesterday raises more suspicion than one with a history.
- Target volume. Two weeks are enough for 20 emails a day; 50 a day needs a month.
- Recipients' mailbox providers. Gmail and Outlook are stricter with new senders in B2B; Mail.ru and Yandex are stricter with bulk mail sent without consent.
How to warm up: manually or automatically
There are two ways. Automatic warm-up is faster and more stable; manual works for one or two mailboxes.
| Method | How it works | Pros | Cons |
|---|---|---|---|
| Manual | You email colleagues, partners and contacts and ask them to reply | Free, natural correspondence | Slow, doesn't scale past 10 mailboxes |
| Automatic (warm-up network) | A service exchanges emails with other mailboxes in the network: opens them, replies, moves them out of spam | Steady volume, works for dozens of mailboxes | Requires a service; quality depends on the network |
| Pre-warmed mailboxes | You get mailboxes that have already been warmed up | Start outreach without waiting | You must respect the limits or reputation drops |
In Holymailer, mailboxes are created on new domains with SPF, DKIM and DMARC already configured, and then go through warm-up. You see the recommended volume for each mailbox in your dashboard, so you don't have to guess the limits.
How many emails per day to send during warm-up
Start with 5–10 emails a day and increase by no more than 20–30% at a time. A sudden jump in volume is the strongest signal for a spam filter, even when all technical records are in order.
Count every email the mailbox sends, not just the cold ones. If a mailbox sends 30 warm-up emails and 40 cold emails, its load is 70 emails a day.
Which metrics to watch during warm-up
Watch five indicators. If any of them crosses the threshold, stop increasing the volume.
- Inbox placement. Check with test emails to your own mailboxes on Gmail, Yandex and Mail.ru.
- Spam complaints. Google requires a rate below 0.3%, ideally below 0.1%. Holymailer recommends no more than 0.1% for cold campaigns.
- Bounces. A hard bounce rate above 2–3% points to a dirty list, not to warm-up.
- Domain reputation in postmaster tools. Connect Gmail Postmaster Tools, Yandex Postmaster and Mail.ru Postmaster.
- Replies. Real replies are the strongest positive signal for filters.
Why a warmed-up mailbox lands in spam again
Warm-up doesn't give you a reputation forever. You can lose it in a few days.
- Exceeding the limit. After warm-up you sent three times more emails than in the last week.
- A dirty list. Lots of non-existent addresses and spam traps.
- Stopping warm-up. Warm-up was switched off right after launch, and the reply rate dropped.
- Identical text. Hundreds of identical emails with the same link look like a bulk mailing.
- Your main domain. Cold emails from the corporate domain put the reputation of the whole company's email at risk.
More on the causes in “Email Deliverability”.
28-day email warm-up schedule
The schedule is for one new mailbox on a separate domain with SPF, DKIM and DMARC configured. The numbers are a benchmark for B2B cold outreach; if your metrics are worse than the thresholds, stay at the current step for another week.
| Days | Warm-up emails per day | Cold emails per day | What to do |
|---|---|---|---|
| 1–3 | 5 | 0 | Add a signature and avatar, send 2–3 emails to colleagues |
| 4–7 | 10 | 0 | Check inbox placement in Gmail, Yandex, Mail.ru |
| 8–14 | 15–20 | 5–10 | First cold emails — to your most accurate segment |
| 15–21 | 20–25 | 15–25 | Connect postmaster tools, check complaints and bounces |
| 22–28 | 20–30 | 30–40 | Reach working volume, keep warm-up running |
| After day 28 | 10–20 | up to 40–50 | Keep background warm-up on permanently |
Stop signals — stop increasing volume if:
- Test emails go to spam at any major provider.
- Spam complaints are above 0.1%.
- Hard bounces are above 3%.
- Domain reputation in Gmail Postmaster Tools has dropped to Low or Bad.
- Open rate has halved compared with last week.
Checklist before you start warm-up:
- A separate domain for outreach, not the company's main domain.
- SPF, DKIM, DMARC and MX records configured.
- No more than 4 mailboxes per domain.
- The mailbox has a sender name, signature and avatar.
- The list has been checked with a validator.
Frequently asked questions
Can I skip warming up a mailbox?
Yes, if you write 5–10 emails a day to people you know. For cold outreach without warm-up, your emails will almost certainly land in spam in the first week. Repairing a damaged reputation takes longer than warming up a mailbox from scratch.
How long does email warm-up take?
At least 7 days; for cold outreach, 3–4 weeks. It depends on domain age and target volume: reaching 40–50 emails a day takes about a month.
Do I need to warm up the domain separately from the mailbox?
Yes, both the domain and the mailbox have a reputation. If a domain has several mailboxes, warm them up in parallel: the domain's total volume should also grow gradually.
Should I keep warming up after the campaign launches?
Yes. Background warm-up of 10–20 emails a day keeps open and reply rates up when cold emails get little response. If you switch it off, reputation starts to decline.
How many cold emails per day can a warmed-up mailbox send?
The benchmark is 30–50 emails a day per mailbox. For larger volumes, add mailboxes and domains instead of loading more onto one mailbox.
What should I do if a mailbox lands in spam during warm-up?
Pause cold emails, drop the volume back to last week's level and run warm-up only for 1–2 weeks. Check SPF, DKIM and DMARC, bounces and complaints. If domain reputation in postmaster tools is Bad, it's easier to replace the domain.
Sources
- Google: Email sender guidelines — in force since February 1, 2024.
- Mail.ru: technical requirements for mailings (in Russian) — complaint thresholds by volume.
- Google Workspace: sending limits.
- Holymailer: how we maintain deliverability (in Russian).
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