AWS SMTP inboxes
built for cold email scale.
$1/inbox/mo. Recommended warm-up period: 2 days.
Use AWS Private IPs, subdomain sending, 10 inboxes per domain, and SMTP/IMAP credentials that plug into your sequencer without OAuth resets.
That's about 3 cents per day per inbox
How Your Emails Get Delivered
AWS SMTP routes through AWS Private IPs with aligned SPF, DKIM, and DMARC — clean routing, fewer moving parts.
Sending Tool
Instantly, Smartlead...
AWS Private IPs
US-based routing
Authenticated DNS
SPF, DKIM, DMARC
Recipient Inbox
Primary tab
AWS Private IPs, SMTP/IMAP credentials, and aligned authentication. Built for outbound instead of internal email.
Strong business email suite, but OAuth, tenant rules, and account policy can add friction for cold outbound.
Trusted inbox provider, but expensive at scale and more sensitive to cold email patterns and bulk account behavior.
Why SimpleInboxes AWS SMTP
Why SMTP?
Google and Microsoft are productivity suites that can send cold email. SimpleInboxes AWS SMTP is outbound infrastructure built for scale, cost control, subdomain flexibility, and faster campaign launches.
AWS Private IPs
US-based routing with private AWS IPs, so your outbound lane is not tied to shared Google or Microsoft policy risk.
2-Day Warm-Up
Move from setup to live campaigns faster. SMTP warms in about 48 hours instead of waiting through a long Google or Microsoft ramp.
Subdomain Sending
Use sending subdomains to stretch each root domain further, separate campaigns, and reduce how many fresh domains you need to buy.
10 Inboxes Per Domain
Run 10 inboxes on one domain instead of spreading the same volume across a pile of new domains.
15-20 Sends Per Inbox
A practical cold outbound range per inbox once warmed, with enough volume to scale without forcing reckless sending patterns.
Cheaper Domains, Too
Subdomains plus 10 inboxes per domain means fewer root domains required. The savings are bigger than the $1/inbox price alone.
The dedicated SMTP argument
Stop buying productivity accounts for an outbound job.
Dedicated SMTP vendors frame the shift the same way: fewer mailbox limits, less OAuth friction, lower cost at scale, and infrastructure that is actually designed for cold email.
See How Much You'll Save
AWS SMTP costs less per inbox and needs fewer domains. The savings compound fast.
At 100 inboxes, AWS SMTP saves you 0 /year vs Microsoft 365
That's $151/mo back in your pocket. Plus 24 fewer domains to manage.
SMTP vs OAuth — Why AWS SMTP Is Simpler
AWS SMTP (What you get)
- Paste SMTP credentials into your sending tool
- No OAuth tokens to refresh or expire
- No two-factor authentication prompts
- No reconnection flows when tokens break
- Bulk upload hundreds of inboxes instantly
- Native inbox access still available
- Works with every sending tool — zero config
OAuth Providers (The headaches)
- OAuth tokens expire and disconnect inboxes
- Two-factor prompts block bulk connections
- Manual re-auth required per inbox
- Sending tools lose connection randomly
- Can't bulk upload — one inbox at a time
- Google requires app passwords or OAuth dance
- Microsoft tokens expire every 90 days
AWS SMTP at a Glance
Flat rate, any volume
3x more than MS/Google
vs 14-day guidance for others
per warmed inbox
The Domain Math
With 10 inboxes per domain, you buy fewer domains. Domain costs are separate — a .com is typically ~$12.99/yr.
10
inboxes per domain
AWS SMTP
3
inboxes per domain
Microsoft
3
inboxes per domain
For 1,000 inboxes: AWS SMTP needs 100 domains vs 334 domains for Microsoft/Google. That's $3,040 saved on domains alone every year.
Subdomains stretch that math even further.
Use lanes like mail.client.com, outbound.client.com, or reply.client.com instead of buying a new root domain for every campaign.