Most B2B cold email campaigns don't fail because of bad copy. They fail because the email never reaches the inbox. Since Google and Yahoo tightened their bulk-sender rules in 2024, and Microsoft followed in 2025, deliverability has become the first thing to fix — not the last.
This playbook covers what we set up before a single outreach email is sent.
1. Never send cold email from your main domain
If your cold campaign hurts your domain reputation, your invoices, proposals and support replies start landing in spam too. Use secondary domains that look like your brand (for example getcompany.com or company-team.com) and redirect them to your main website.
- 2–3 sending domains for a small campaign
- 2–3 mailboxes per domain
- Real names on every mailbox, never
info@orsales@
2. Authenticate every domain: SPF, DKIM and DMARC
These three DNS records prove you are who you say you are. Without them, major providers now reject or spam-folder your mail.
| Record | What it does | Minimum setup |
|---|---|---|
| SPF | Lists the servers allowed to send for your domain | One SPF record, under 10 DNS lookups |
| DKIM | Signs each email cryptographically | 2048-bit key from your email provider |
| DMARC | Tells receivers what to do if checks fail | Start with p=none, move to p=quarantine |
Also set up a custom tracking domain if you track clicks, so you don't share a reputation with thousands of other senders.
3. Warm up before you send
A brand-new mailbox that suddenly sends 200 emails a day looks exactly like a spammer. Warm each mailbox for 2–4 weeks, starting at a handful of emails per day and increasing gradually.
Rule of thumb: keep each mailbox under 30–50 cold emails per day, even after warm-up. Scale by adding mailboxes, not by pushing volume.
4. Keep your spam complaint rate under 0.1%
Google's guidelines ask senders to stay below 0.3% spam complaints and recommend staying under 0.1%. In cold outreach, the fastest way to get complaints is to email people who have no reason to hear from you. That's why targeting is a deliverability tactic, not just a sales tactic.
5. Verify every list
Bounces are a strong negative signal. Before any campaign:
- Verify every email address with a verification tool
- Remove catch-all and role-based addresses where possible
- Aim for a bounce rate under 2%
6. Write emails that look like one person writing to another
Spam filters and humans react to the same things. Keep emails:
- Short — 50 to 120 words
- Plain text — no images, heavy HTML or attachments in the first email
- Light on links — ideally zero or one in the first touch
- Personal — a specific reason why you're writing to this company now
7. Make it easy to say no
Include a simple way to opt out ("Not relevant? Just reply and I won't follow up"). It lowers complaints, protects your domain, and it's required under laws like GDPR and CAN-SPAM.
8. Monitor weekly
Use Google Postmaster Tools for Gmail recipients, watch your bounce and reply rates, and run placement tests. If open or reply rates drop suddenly, pause and investigate before sending more.
The checklist
- Secondary domains and real-name mailboxes
- SPF, DKIM and DMARC on every domain
- 2–4 week warm-up
- Under 50 emails per mailbox per day
- Verified lists, under 2% bounce
- Short, plain-text, personal emails
- Clear opt-out
- Weekly monitoring
Get these right and your copy finally gets the chance to do its job.