Cold Email Inbox Setup Checklist for New Agencies in 2026
By Puzzle Inbox Team · May 22, 2026 · 10 min read read
Launching a cold email agency in 2026? This setup checklist covers domains, inbox providers, DNS, warmup, and tooling with prices for a 100-inbox stack.
A new agency setting up cold email inboxes in 2026 should budget $250-$400/month for a 100-inbox stack across 25-33 domains, with full SPF/DKIM/DMARC, 14-day warmup, and placement monitoring in place before any campaign sends.
Skipping steps on inbox setup is the fastest way to torch a new agency. This checklist is what we run for every new client onboarding — in order, with real prices and named providers.
Step 1: Buy secondary domains
Never send cold from your main domain. Register 25-33 lookalike domains at Cloudflare ($10/year) or Porkbun ($9/year). Pattern: try-yourbrand.com, get-yourbrand.com, hello-yourbrand.io. Budget: $250-$330/year, or about $25/month amortized.
Step 2: Pick an inbox provider
For agency volume, the per-inbox economics matter. Top three for 100-inbox setups:
- Mailforge: $125/month at $1.25/inbox
- Maildoso: $200/month at $2/inbox, warmup included
- Hypertide: $199/month, US IPs
Mailforge wins on raw cost; Maildoso wins if you do not want to manage warmup separately.
Step 3: DNS configuration
For every domain, set these records before any inbox is used:
- MX: pointing to provider's mail servers
- SPF: v=spf1 include:provider.com ~all
- DKIM: 2048-bit key, published as TXT
- DMARC: v=DMARC1; p=none; rua=mailto:reports@yourdomain.com (move to p=quarantine after 30 days)
- BIMI (optional): for brand logo in Gmail, requires VMC certificate
Most modern providers auto-publish these via Cloudflare API. If yours does not, budget 30-60 minutes per domain manually.
Step 4: Domain forwarding
Forward each secondary domain to your main site with a 301 redirect. Prospects who paste the domain into a browser should land on your real homepage, not a 404. Cloudflare Page Rules handle this free.
Step 5: Reply-handling mailbox
You need one Google Workspace mailbox ($7/month) per agency or per client to receive replies. Forward all secondary-domain inboxes to it. Without this, you lose replies to spam folders on the sending infrastructure.
Step 6: Warmup
Run automated warmup for 14-21 days before sending real campaigns. Start at 5 sends/day per inbox, ramp 5/day until reaching 30-40/day cap. Built-in warmup from Smartlead or Instantly handles this with 2,000+ warmup network peers.
Step 7: Placement monitoring
Spin up Puzzle Inbox or similar to track Primary vs Promotions vs Spam placement across Gmail, Outlook, and Yahoo. Free tier covers basic checks; paid tiers ($49-$99/month) add per-inbox alerts. Without monitoring, you will not know deliverability is degrading until reply rates drop two weeks later.
Step 8: Sender tool
Pick from the best cold email software roundup. For 100 inboxes, expect $97-$199/month. Smartlead's $97 plan handles 100+ inboxes with rotation and reply detection.
Step 9: Pre-launch verification
Before pressing send on a real campaign:
- Send 10 test emails per inbox to seed accounts
- Verify SPF pass, DKIM pass, DMARC alignment
- Confirm Primary placement above 80%
- Confirm reply forwarding works end-to-end
- Verify unsubscribe link renders correctly
Step 10: First send
Start at 50% of max volume for the first week. Watch bounce rate (under 3%) and spam complaint rate (under 0.1%). If either breaches, pause and audit list quality before resuming.
Full 100-inbox monthly budget
- Inboxes (Mailforge): $125
- Domains (33 amortized): $25
- Reply mailbox (Workspace): $7
- Sender (Smartlead): $97
- Placement monitoring: $49
- Total: $303/month
At 3,000 sends/day, that is 65,000 sends/month for about $0.005 per send — well below cost-per-touch on any other channel.