Most cold email agencies charge $5,000–$10,000 per month – yet almost none clearly explain what you’re actually paying for.
Here’s the uncomfortable truth:
The infrastructure required to send 2,500 cold emails per day using Google Workspace costs under $1,800/month.
So where does the rest of the money go?
In this post, we’ll break down:
- The exact infrastructure required to send 50,000 emails per month safely
- The true monthly cost, line by line
- Why most campaigns fail (and why it’s not infrastructure)
- When it actually makes sense to pay an agency – and when it doesn’t
No fluff. No theory. Just numbers.
Cold Email Volume Explained (2,500 Emails Per Day)
To understand cost, we need to understand how modern cold email actually works.
Target volume:
- 2,500 emails per day
- 20 working days per month
- 50,000 emails per month
This is a standard volume for B2B outbound that balances scale and deliverability.
The Infrastructure Setup (This Is What Agencies Don’t Show You)
Email Sending Architecture
To safely send 2,500 emails per day using Google Workspace:
- 42 sending domains
- 3 Google Workspace mailboxes per domain
- 126 mailboxes total
- 20 emails per mailbox per day
That equals:
126 × 20 = 2,520 emails/day
This setup mimics a small outbound sales team – not a spam operation.
Why 3 Mailboxes Per Domain Is the Sweet Spot
- 1–2 mailboxes per domain → looks unnatural
- 5+ mailboxes per domain → looks like a cold email farm
- 3 mailboxes → appears like a legitimate business team
Google’s filters care more about patterns than volume.
Infrastructure Cost Breakdown (Monthly)
1. Domains
- 42 domains × $24.50/year (AUD) = $1029/year (AUD) (.com domains ONLY) (pricing from Cheaper Domains non-affiliated)
- Monthly cost: $85.75
Pro tip:
Use .com.au domains at ~$16/year instead.
- 42 × $16/year = $672/year
- Monthly cost: $56
- Savings: $29.75/month
- Deliverability impact: none (tested extensively at 2%+ reply rates)
2. Google Workspace Mailboxes
- 126 mailboxes × $9.90/month (AUD) – it’s Australia it’s more expensive than the US and UK.
- $1247.40/month (AUD)
3. Email Validation (Non-Negotiable)
- 50,000 emails/month
- ~$4 per 1,000 validations
- ~$200/month
Tools:
Skipping validation is the fastest way to burn domains.
All work fine.
Choose based on UI, not “features”.
5. Data Enrichment & Workflows
Typical stack:
Total Infrastructure Cost
| Setup | Monthly Cost |
|---|
| Using .com domains | ~$1733.15/month |
| Using .com.au domains | ~$1703.4/month |
That’s it.
That’s the entire infrastructure agencies use.
Expected Results at This Volume
Monthly volume:
Reply rate scenarios:
1. Average campaign (1.5% reply rate)
- 750 replies
- 15% positive replies
- ~113 engaged leads/month
2. Weak copy (<1% reply rate)
- ~75 engaged leads
- Usually blamed on “deliverability” (it’s not)
3. Strong copy (2%+ reply rate)
What Actually Determines Reply Rate
Infrastructure just keeps you alive. It doesn’t win.
Reply rate drivers:
- List quality: 60%
- Offer: 30%
- Copy: 10% (it’s important but it’s not everything)
Infrastructure is binary:
- Get it right → campaign lives
- Get it wrong → everything dies
Google Workspace Sending Limits (What Actually Matters)
- 20 emails per mailbox per day = safe baseline
- Can push to 25–30 after warm-up (higher risk)
Recommended ramp schedule:
- Warmup: 21–28 days
- Weeks 1–2: 5–10 sends/mailbox
- Week 3: 15 sends
- Week 4+: 20–25 sends
Rushing this kills domains.
Domain Myths (What Doesn’t Matter)
- Registrar: Namecheap, Porkbun, GoDaddy – irrelevant
- Extension: .info, .com, .com.au, .co – same performance
- Domain age: fresh domains work fine
- Warm-up time: 21–28 days is enough
What Destroys Cold Email Infrastructure Fast
- Skipping validation
- 10–15% bounce rate = dead domains in days
- Replacement cost: $800–$1,200 + 3 weeks lost
- Sending too much per mailbox
- 30+ daily sends → flagged within ~2 weeks
- Too many mailboxes per domain
- 5+ looks automated, not human
- Bad lists
- Reply rate <0.5% = ESPs treat you as spam
When You Should Scale Beyond 2,500 Emails/Day
Only scale when:
- Reply rate is consistently above 1.5%
Scaling options:
- Add more domains (84 domains = 5,000/day)
- Move to custom SMTP for higher throughput
Scaling bad copy just multiplies losses.
The Hidden Costs Agencies Don’t Mention
Infrastructure isn’t the expensive part.
Execution is.
Time costs per month:
- Initial setup: 5–8 hours
- Ongoing management: ~10 hours
- Reply handling: 10–20 hours
- List building & enrichment: 10–15 hours
Total:
20–30 hours/month minimum
That’s what you’re really paying agencies for.
The Real Takeaway
- Cold email infrastructure for 2,500 sends/day costs ~$900/month
- Agencies charging $5–10k/month are selling:
- Execution
- Experience
- Systems
- Risk reduction
- Margin
If you have time, discipline, and patience, you can absolutely run this in-house.
If you don’t? That’s where agencies earn their keep.