If you’ve ever tried sending cold emails at scale, you’ve probably run into one of these problems:
- Emails land in spam (or worse — never deliver)
- Gmail limits your sending
- You get domain blacklisted
- You spend hours manually managing inboxes
I used to hit all of those walls — until I discovered a smarter system using Instantly.ai.
Here’s exactly how I sent 5,000 cold emails in a single week, maintained a 65% open rate, and landed 8 qualified meetings, all without getting flagged.
🚨 First, The Mistake Most People Make
Most people try to scale too fast or send from their personal Gmail account. That’s a quick path to disaster. Here’s why that fails:
- Gmail and Outlook have sending limits (typically 500–2,000/day)
- New inboxes need to “warm up” before bulk sending
- Spam filters look for volume spikes and copy-paste templates
- No inbox rotation = all eggs in one basket
💡 Rule #1: You can’t scale cold outreach without the right tech stack.
🧰 The Exact Tech Stack I Used
Here’s what I used to make 5,000 emails/week possible — safely:
✅ Cold Email Platform: Instantly.ai
- Smart inbox rotation
- Built-in warm-up
- Campaign automation
- Easy UI for tracking
✅ Email Hosting: Google Workspace
- 3 custom domains
- 3 inboxes per domain (9 total)
- Each inbox cost ~$6/month
✅ Domain Setup: Namecheap + SPF/DKIM/DMARC
- Each sending domain configured with:
- SPF
- DKIM
- DMARC
- Verified inside Instantly
🧪 Step-by-Step Setup
Step 1: Bought 3 alternate domains
I didn’t want to risk my main domain (example: brandhq.com). Instead, I registered:
- brandhq-mail.com
- brandhq-tools.com
- brandhq-outreach.com
Step 2: Created 9 sending inboxes
Each domain had 3 emails:
- hello@
- contact@
- team@
All created in Google Workspace and connected to Instantly.
Step 3: Activated warm-up for 10 days
Instantly’s built-in warm-up sent low-volume, human-like emails between inboxes and other users on the platform.
Pro tip: Don’t skip this. It keeps your reputation safe and trains spam filters to trust you.
Step 4: Wrote 3 personalized templates
- Short, plain-text
- Custom first line
- No images, no links in the first email
- Follow-ups spaced 3 days apart
Step 5: Set volume to 50–70 emails/day/inbox
With 9 inboxes sending ~60/day, that’s 540/day total. In one week: 5,000+ emails
📊 Results After 7 Days
| Metric | Value |
|---|---|
| Emails Sent | 5,160 |
| Open Rate | 65.2% |
| Reply Rate | 6.8% |
| Positive Replies | 28 |
| Meetings Booked | 8 |
| Spam Complaints | 0 |
⚠️ Common Pitfalls to Avoid
- Sending too much, too soon → Always warm up first
- Using the same message for everyone → Personalize intros at minimum
- Link-heavy templates → Avoid links in your first email if possible
- Skipping SPF/DKIM setup → Your emails will go straight to junk
✅ Why I Chose Instantly.ai
After testing multiple platforms, here’s why I stuck with Instantly:
- Unlimited sending with inbox rotation
- Built-in warm-up (saves $30+/mo per inbox)
- Super easy to use — no learning curve
- Open/click tracking built-in
- Affordable — just $37/month
It’s honestly the best tool I’ve found for high-volume, deliverability-focused cold outreach.
🎯 Want to try it yourself?
Click here to start your Instantly.ai 14-day free trial →
💡 Final Thoughts
Sending cold email at scale isn’t about spamming — it’s about smart systems, clean domains, and steady growth.
If you’re a freelancer, founder, or consultant trying to grow without paid ads, cold outreach is still one of the best ROI channels out there.
Just make sure you’re doing it right — and using the right tools.