What Not To Do
Email warm-up is the process of gradually increasing your sending volume from a new domain so that mailbox providers like Gmail and Outlook learn to trust you before you start blasting prospects. Skip this step and you're not just risking the spam folder — you're risking losing the domain entirely.
Do not blast thousands of emails from a new domain immediately. Google recommends aiming for a spam rate around 0.1% (1 in every 1,000 emails). If your rate climbs to be multiple times above 0.3% — that's multiple times above 3 in every 1,000 — Google can automatically ban the individual sender and potentially lock down your entire domain. That caveat matters: it's not just crossing 0.3% that triggers the hammer, it's sustained rates well above it.
One important nuance: Google's February 2024 sender guidelines technically target bulk senders sending 5,000+ messages per day to personal Gmail accounts. According to Revenue Wizards, the rules don't apply to emails sent to Google Workspace addresses — meaning direct B2B outbound is not formally impacted. That said, they explicitly recommend B2B senders follow the same principles anyway, because the underlying deliverability mechanics are the same and the domain-ban risk is real regardless.
Another common mistake is skipping authentication. Before you send a single warm-up email, you need SPF, DKIM, and DMARC all configured correctly. Google and Yahoo made DKIM and DMARC mandatory for senders starting February 2024. Revenue Wizards also recommends adding a one-click unsubscribe link and avoiding tracking pixels, both of which can quietly tank your sender reputation.
Finally, don't use your primary company domain for outbound. Set up a dedicated sending domain (e.g., if your main domain is @company.com, use something like @company.so for sales outreach). That way, if something goes wrong, your core domain stays clean.
The Correct Move
Your sender reputation — the score mailbox providers assign based on your sending history and how recipients engage with your emails — is the single most important factor affecting whether your emails land in the inbox or disappear forever. You build it slowly, on purpose.
Here's the multi-step approach that actually works:
- Complete your technical setup first. SPF, DKIM, DMARC, and ARC authentication must all be in place. Add a one-click unsubscribe. Keep your HTML signature minimal — no excessive images or links. Do this before you send anything.
- Use a warm-up tool and give it time. Warm-up tools work by sending emails from your account to a network of safe inboxes that automatically open, reply, and sometimes mark your messages as important — mimicking the behavior of a healthy, trusted sender. Plan for at least 2–4 weeks of warm-up before running real campaigns; for a brand-new domain, many practitioners recommend 8–12 weeks.
- Keep daily volume low. Revenue Wizards recommends capping outbound at fewer than 50 emails per day per person during this period to avoid triggering spam detectors. Avoid sending large batches at once.
- Monitor your spam rate actively. Use Google's Postmaster Tool to track how many of your emails are being reported as spam. Strive to stay well under 0.1%.
On tool selection: Instantly.ai is a commonly recommended option for all-in-one outreach and warm-up. One competitor comparison table (published by Salesso, itself a cold email platform) lists Instantly.ai's deliverability score at 95% — but note that these are vendor-reported figures from a competing tool's own marketing content, not independently verified rates. Treat them as a rough signal, not gospel, and cross-reference with neutral third-party reviews before committing to any platform.
The payoff for doing this right is real access to the inbox. Rushing it just means your carefully written cold emails never get read.