Email warm-up is how you build trust for a new sending domain before it carries real outreach. A new domain has no sending history. To Gmail, Outlook and Yahoo it looks exactly like a domain a spammer registered yesterday. Warming up means building a short, clean track record before you ask that domain to carry real cold outreach to distributors and importers.
This guide assumes you already have a separate sending domain and mailboxes. If not, start with our Cold Email Deliverability Checklist for Exporters and come back here.
Before you send anything
Warm-up cannot fix a broken setup. Check these first, on every sending domain:
- SPF, DKIM and DMARC records are published and passing. Gmail asks senders to set up SPF and DKIM first, then add a DMARC policy.
- The domain redirects to your real website, so a buyer who checks it lands somewhere credible.
- Each mailbox belongs to a real person with a name, photo and signature. Generic addresses like
sales@warm up worse and convert worse. - Tracking is minimal. Turn off open tracking pixels and link tracking during warm-up if your tool allows it.
- Google Postmaster Tools is set up for the domain, so you can see what Gmail sees.
Email warm-up schedule, week by week
The numbers below are cold emails per mailbox per day. They are a conservative starting point, not a rule. Vendors publish different schedules; what they agree on is starting small, growing gradually and never jumping.
| Week | Cold emails per mailbox per day | What to do |
|---|---|---|
| 1 | 0 | Automatic warm-up only, or a handful of real conversations with colleagues, partners and existing contacts who will reply |
| 2 | 5–10 | First real outreach to your best-fit, verified contacts. Keep warm-up running in the background |
| 3 | 10–20 | Add a follow-up step. Watch bounces and replies daily |
| 4 | 20–30 | Widen to the rest of your list for this market |
| 5–6 | 30–40 | Hold here if anything looks off; otherwise keep growing slowly |
| 7+ | Up to about 50 | Your steady state. To send more, add mailboxes, not volume |
Gmail's own guidance for senders who hit delivery problems points the same way: drop below the level where trouble started, then increase gradually, commonly 25% to 100% per day depending on your situation. For a new domain, sit at the lower end.
Do you need an email warm-up tool?
Most cold email platforms include an automatic warm-up feature, and standalone email warm-up tools exist too. They send messages between mailboxes in a shared network, open them, reply and pull them out of spam, so a new mailbox shows normal activity early.
- They help with the first weeks, when you have no real conversations yet.
- They do not replace real engagement. Replies from actual buyers matter more than activity inside a warm-up network.
- Keep warm-up running at low volume after you start real outreach, rather than switching it off abruptly.
- Check what you pay for. Warm-up is often included in a cold email tool's plan, so a separate subscription may not be needed.
We will cover specific warm-up tools in separate reviews once we have tested them.
Keep the sending pattern boring
Mailbox providers trust senders who behave consistently. Gmail specifically warns against bursts, such as sending dozens of emails at once and then nothing, and says steady volume matters most for new domains.
- Send every working day, not in bursts once a week.
- Spread sends through the day. Most cold email tools let you set a random gap of several minutes between emails.
- Send in your buyer's working hours. A sequence to Germany should go out in the German morning, not at 3 a.m. from Wuhan.
- Spread volume across mailboxes. Five mailboxes sending 30 emails each look far healthier than one mailbox sending 150.
Warm up with the right list
The contacts you email in the first weeks shape your reputation more than anything else.
- Verify every address. Bounces are one of the strongest negative signals, and a new domain has no goodwill to absorb them.
- Start with your warmest segment: buyers who visited your trade show booth, distributors who asked for a catalog last year, contacts who are clearly a fit for your product.
- Save the long shots for later. Large, loosely targeted lists from a database belong in week five or six, if at all.
- Avoid shared inboxes such as
info@andpurchasing@. They are read by many people, rarely reply and are more likely to report you.
Watch these signals every week
| Signal | Where to see it | Healthy | Slow down when |
|---|---|---|---|
| Spam complaint rate | Google Postmaster Tools | Below 0.1% | It rises toward 0.1%; 0.3% is Gmail's hard limit for bulk senders |
| Bounce rate | Your cold email tool | Close to zero | Above a few percent: stop and clean the list |
| Deferrals and blocks | Your tool's error log (4xx and 5xx codes) | None | Any repeated "rate limited" or "try again later" errors |
| Reply rate | Your cold email tool | Steady or rising | A sudden drop to zero can mean you are in spam |
| Compliance status | Google Postmaster Tools | Pass on every check | Any "needs work" result |
Google has been rolling out a new version of Postmaster Tools that replaces the old domain and IP reputation charts with a compliance status view. Spam rate, authentication and delivery error reports are still there. Microsoft offers a similar program for Outlook.com called SNDS, which is mainly useful if you send from your own IP addresses.
If something goes wrong
- Spam complaints climbing: pause new outreach on that domain, review your list source and your first email, and restart at half the volume.
- Bounce spike: stop the campaign, re-verify the list, remove every hard bounce and find out where the bad addresses came from.
- Deferrals ("try again later"): Gmail suggests pausing briefly, confirming that a single message gets through, then staying below the problem level for a day before increasing again.
- Replies stop completely: send a test to a few personal Gmail and Outlook addresses you control and check where it lands.
Recovering a damaged domain takes weeks. This is why most teams treat sending domains as replaceable and keep their main domain out of cold outreach entirely.
Quick checklist
- Separate sending domain, redirected to your website, a few days old
- SPF, DKIM and DMARC passing; Postmaster Tools connected
- Real names and signatures on every mailbox, tracking off during warm-up
- Week 1 warm-up only, then real outreach starting at 5–10 per mailbox per day, following the email warm-up schedule above
- Verified, best-fit contacts first; no shared inboxes
- Steady daily sending in the buyer's time zone, spread across mailboxes
- Spam rate below 0.1%, bounces near zero, no repeated deferrals
- Steady state around 50 cold emails per mailbox per day; scale with more mailboxes
Sources
- Gmail Help: Top 10 Gmail sender issues (gradual volume increases, consistent sending, spam rate, authentication)
- Blueshift: Google Postmaster Tools v2 and the compliance dashboard (what changed from the old reputation charts)
- Smartlead: How many cold emails per day (per-mailbox and per-domain ceilings)
- Zeliq: Email warm-up protocol for B2B cold email (an example of a six-to-eight-week vendor schedule)
FAQ
How long does it take to warm up a new domain?
Plan on four to eight weeks before a new domain carries your full cold email volume. Some vendors suggest six to eight weeks for a first warm-up. Going faster is possible, but every shortcut raises the chance that your first real campaign lands in spam.
Do I still need to warm up if I use a cold email tool with automatic warm-up?
Yes, the tool only automates part of it. Automatic warm-up sends and replies to messages between mailboxes in a shared network, which builds early activity. You still need to keep real outreach volume low at first, send consistently and watch your bounce and spam rates yourself.
How many cold emails can one mailbox send per day after warm-up?
A common ceiling in the cold email industry is about 50 cold emails per mailbox per day, and a few hundred per sending domain. To send more, add mailboxes and domains instead of pushing one mailbox harder.
Can I warm up my main company domain instead of buying a new one?
You can, but most export teams keep their main domain out of cold outreach. If a campaign goes wrong, a damaged reputation on your main domain also hurts quotes, invoices and replies to existing customers.
Silas Xiao
Builds websites, runs Google SEO and LinkedIn outreach for B2B manufacturers selling into Central Asia, Russia, Southeast Asia and the US. Every tool on ExportBench is tested on that day-to-day work before it gets a verdict.
