Setting up cold email infra that doesn't get you burned

If you’re sending cold emails without thinking about your infrastructure… you’re already behind.

Deliverability doesn’t start with your subject line - it starts with your domain, your mailbox provider, your IP address, and how you’ve configured them.

And if that foundation is weak? No copy, no follow-up, no personalization hack will save you. You’ll end up in spam, or worse - silently blacklisted with no idea why your reply rates dropped to zero.

Here’s how to build infrastructure that actually works - and scales with you.

1. Always use secondary domains for outreach

Your primary company domain (like yourcompany.com) is for your brand, your website, and transactional emails - not for cold outreach.
Cold email campaigns increase your risk of getting flagged or blocklisted. If you burn your main domain, you damage your reputation across all channels.

What to do instead: Register secondary domains (like yourcompanymail.com or tryyourcompany.com) and use them specifically for outbound.

Need help generating domain ideas? Try our free Cold Email Domain Generator.

2. Authenticate everything

If your domain isn’t authenticated, your emails look suspicious to ESPs - even before a human sees them.

Set up:

• SPF (Sender Policy Framework) to define which servers can send on your behalf

• DKIM (DomainKeys Identified Mail) to confirm message integrity

• DMARC to tell inboxes how to handle failed authentication

You’d be surprised how many people skip this - and get filtered because of it. Tools like Mailforge, Infraforge and Primeforge handle all of this automatically.

3. Warm up mailboxes before you send

Brand new domains and mailboxes are cold - and cold means risky. You can’t just create an inbox and start blasting sequences.

You need to simulate normal, human email behavior first - sending and receiving emails gradually over time. This warms up the reputation of the domain and IP in the eyes of Gmail, Outlook, etc.

Warmforge automates the entire process, and you also get 1 free warm-up slot & 1 free placement test per month to get you started.

4. Match the ESP to your prospect list

If most of your prospects use Gmail, you’ll get better inbox placement if you send from Gmail. Same goes for Outlook.

This is called ESP matching - and it matters more than you think.

Start by running a few of your leads through our free ESP Checker. Then build your infrastructure to reflect the breakdown - Gmail mailboxes for Gmail prospects, Outlook for Outlook, etc.

Primeforge makes this ridiculously easy, offering both Google Workspace and Microsoft 365 mailboxes - fully warmed up, configured, and deployed on U.S. IPs.

5. Run inbox placement tests regularly

Deliverability can change fast - even if your setup was great last month. A bad domain, blacklisted IP, or volume spike can push you into spam.

That’s why inbox placement tests are critical.

They simulate sending emails to test inboxes across Gmail, Outlook, Yahoo, and others to show where your messages are actually landing: inbox, promotions, spam, or blocked entirely.

With Warmforge, you get 1 free placement test per month - use it. It’s one of the best early warning systems you can have.

If you’re building infrastructure manually, you’re wasting hours on DNS, warming up inboxes, checking IPs, and chasing down errors.

Primeforge does it for you - at scale. We’re launching Primeforge on Product Hunt - and we’d love your support. Come check it out, and help us make cold outreach infrastructure smarter, faster, and safer for everyone.