Inbox warmup
Warmup is how a brand-new inbox earns trust before it sends cold email. It starts automatically once your inboxes are built; you don’t have to set anything up. Your job is mostly to be patient and not rush the first campaign.
What warmup is
Section titled “What warmup is”A new inbox has no history, so email providers don’t know whether to trust it. Sending hundreds of cold emails from it on day one looks exactly like a spammer, and filters react accordingly.
During warmup, your inboxes swap ordinary emails with other established inboxes. Those emails get opened and replied to, which builds a track record that tells Gmail, Outlook and others “this is a real sender”. It works a bit like a new employee building a reputation: small, steady, good behaviour first, bigger responsibilities later.
Who does what
Section titled “Who does what”- We connect your inboxes to your sequencer and switch warmup on when we set them up.
- Your sequencer (Instantly, Plusvibe and the like) runs the warmup emails day to day.
- You wait until the inboxes are ready, then start sending within the safe limits.
How long it takes
Section titled “How long it takes”It depends on the inbox type. These ranges come from our Cold Email Bible: the minimum is the earliest it’s reasonable to send your first cold email, the recommended time is what we’d aim for.
| Inbox type | Minimum before cold sending | Recommended |
|---|---|---|
| Outlook Premium | 3 to 5 days | 10 to 14 days |
| Outlook (normal) | 5 to 7 days | 10 to 14 days |
| Google Workspace | 15 days | 20 to 25 days |
| SMTP | 3 to 4 weeks | 4 to 6 weeks, longer is better |
This warmup time is on top of setup, which usually takes 48 to 72 hours after you order.
Starting to send
Section titled “Starting to send”When an inbox is ready, ease into cold sending rather than jumping straight to the full daily limit.
- Start small. A few cold emails per inbox per day in the first week.
- Increase gradually. Add a little each day. Never double your volume from one day to the next.
- Settle at the safe limit for that inbox type. See Safe sending limits.
Do and don’t during warmup
Section titled “Do and don’t during warmup”Do
- Keep warmup running after you start campaigns. It keeps working quietly in the background and helps maintain your reputation.
- Verify your lead list before the first campaign, for example with EmailShield. Bounced addresses hurt a young inbox more than an old one.
- Prepare your copy while you wait. If you’re sending from Outlook, read Writing for Outlook.
Don’t
- Don’t change DNS records. Editing SPF, DKIM or DMARC during warmup resets the trust signals.
- Don’t send a big burst early. A single spike day before an inbox is ready can flag a domain for a long time.
- Don’t turn warmup off when your campaign starts.
Signs something is off
Section titled “Signs something is off”| What you notice | Likely cause |
|---|---|
| Warmup emails are bouncing | A DNS record is set wrong |
| Warmup emails land in spam | A domain reputation problem |
| No warmup activity at all | The inbox connection to your sequencer needs fixing |
In all three cases, message the team in your private Slack channel or through the chat bubble in the app, and include the domain name. Don’t try to fix DNS yourself while warmup is running.