Cold email infrastructure is fragile. New domains and mailboxes have no sending history, so inbox providers watch them closely. Warming them up slowly and keeping your daily volume within safe limits is the best way to stay out of spam. This guide covers how long to warm up, how many emails to send per day, and how to ramp up safely.
Day 1: put every new mailbox into warm-up. Send only warm-up emails, no cold emails.
Weeks 1-2: warm-up starts at around 3-4 emails per day and slowly ramps up. By the end of 2 weeks it reaches 20 warm-up emails per day per mailbox.
After 2 weeks: you can start sending cold emails. Warm-up keeps running in the background, always. Never turn it off.
Cold volume: up to 30 cold emails per day per mailbox. With 20 warm-up emails, that is 50 emails per day per mailbox in total.
Safest ramp: start cold sending at around 15-20 per day and build up to 30 over 1-2 weeks. Starting at 30 on day 15 is also fine.
Warm-up is the process of building a positive sending reputation for a new mailbox. Automated, realistic conversations are sent between your mailbox and a network of other real inboxes. They are opened, replied to, and rescued from spam when needed. This shows inbox providers that your mailbox sends wanted email and gets engagement.
Warm-up emails are separate from your campaigns. They do not count toward the sends in your sequences.
Brand-new mailboxes have no reputation, so sudden volume looks suspicious.
Gmail, Outlook and other providers judge senders on engagement, not only on technical setup.
A mailbox that lands in spam early is slow and expensive to recover.
Ongoing warm-up keeps your reputation positive while your cold campaigns run.
Period | Warm-up emails per day | Cold emails per day |
Days 1-3 | 3-4 | 0 |
Days 4-7 | Rising to about 10 | 0 |
Days 8-14 | Rising to 20 by day 14 | 0 |
First 1-2 weeks of cold sending (after day 14) | 20, keep running | Start at 15-20, build up to 30 |
Steady state | 20, keep running | Up to 30 (50 in total per mailbox) |
The warm-up numbers are a guide. What matters is that the ramp is gradual and reaches 20 warm-up emails per day by the end of the 2 weeks.
We recommend a maximum of 30 cold emails per day per mailbox. Together with 20 warm-up emails, each mailbox sends 50 emails per day in total.
Going above 30 cold emails per mailbox is not recommended. It raises the risk of spam placement and damaged reputation.
To send more, add more mailboxes and domains instead of pushing each mailbox harder. This is called scaling horizontally.
We recommend 2-3 mailboxes per domain. See how many mailboxes you can create per domain.
Example: 10 mailboxes at 30 cold emails per day can send up to 300 cold emails per day, plus warm-up in the background.
Finish the 2 weeks of warm-up with no cold emails.
Start cold sending at around 15-20 emails per day per mailbox, with warm-up still running.
Increase gradually over 1-2 weeks until you reach 30 cold emails per day.
Hold at 30 and scale further by adding mailboxes.
Starting at 30 cold emails per day right at the 2-week mark is also fine. A gradual ramp is simply the safer option.
Warm-up cannot fix a broken setup. Before you start, check that your domains have:
SPF, DKIM and DMARC records set up correctly
Valid MX records
A custom tracking domain
Domain forwarding to your main website
A sender name and profile that match the domain
Inbox providers look at how recipients react to your emails, not only how many you send. Steady daily volume, relevant targeting, and replies and opens all help. Spam complaints, bounces and ignored emails hurt.
Sending cold emails on day 1. New mailboxes should only send warm-up emails for the first 2 weeks.
Turning warm-up off after 2 weeks. Warm-up should run continuously, also while you send cold emails.
Scaling too fast. Jumping from 0 to hundreds of emails per mailbox gets mailboxes flagged. Stay at 30 cold emails per day per mailbox or less.
Poor lead data. Unvalidated emails cause bounces that damage your reputation. Validate your list first.
Inconsistent sending. Long pauses followed by sudden bursts look unnatural. Keep volume steady.
Ignoring inbox health. Watch bounce rates, spam placement and warm-up health, and pause a mailbox that is struggling.
Warmforge is the warm-up tool built for this process. It is natively integrated with Salesforge. Its key features are:
AI-generated, realistic warm-up conversations
Deliverability monitoring and inbox placement testing
Infrastructure validation for your DNS records
Native Salesforge integration, so your mailboxes are warmed up and ready to send in the same place
Pre-warmed Primeforge mailboxes have already been through the initial warm-up. You still need to keep warm-up running and follow the same limit of 30 cold emails per day per mailbox.
Good deliverability comes down to a few habits:
Warm up new mailboxes for 2 weeks with no cold emails.
Keep warm-up running at all times.
Send up to 30 cold emails per day per mailbox, ramping up gradually.
Scale by adding mailboxes and domains, not by sending more per mailbox.
