Warmup Inbox
Warmup Inbox warms mailboxes by sending emails to other users in the network and simulating opens, clicks, and replies. It is similar to Mailreach but cheaper and less feature-rich. Teams use Warmup Inbox when they need basic warmup without paying for Mailreach-level diagnostics or placement testing.
Official site ↗Why it ranks here
Warmup Inbox does one thing well: it warms mailboxes cheaply. The algorithm is simple (less tuning than Mailreach), but it works. It ranks as situational because most serious teams prefer Mailreach or the built-in warmup in Smartlead/Instantly.
Where it sits
Warmup Inbox ranks below Mailreach on features and transparency. It ranks as situational because the lower cost matters for small teams or teams warming many mailboxes. If you only warm 5 mailboxes, Mailreach is better. If you warm 30, Warmup Inbox saves money.
How GTM Engineering teams use it
Engineers connect new mailboxes to Warmup Inbox before launching campaigns. The platform warms them over 2-3 weeks by sending emails to the network. Engineers monitor warmup progress (emails sent, replies received) in the dashboard. Once warmup is complete, they connect the mailbox to their sending platform and launch campaigns.
In-depth notes
Pricing is per-mailbox monthly subscription (cheaper than Mailreach). The warmup algorithm is less transparent (you cannot tune reply rates or cadence), but it works for most mailboxes. No inbox placement testing (you need GlockApps or Mailreach for that). Best for teams on a budget who need basic warmup without diagnostics.
Best for
Teams that need affordable mailbox warmup without advanced diagnostics.
Avoid if
You need placement testing or detailed warmup tuning.
The rest of Sending & deliverability
Smartlead Leader High-volume cold email with mailbox rotation and inbox monitoring. #2 
Instantly Leader Affordable cold email sending with built-in mailbox warmup. #3 
lemlist Strong Cold email with strong personalization (video, images, dynamic landing pages). #4 
Salesforge Strong AI-powered cold email with built-in mailbox and domain provisioning. #5 
QuickMail Strong Simple cold email sending with inbox rotation and basic analytics. #6 
Mailreach Strong Dedicated mailbox warmup and inbox placement testing. #7 
Woodpecker Situational Cold email automation with strong CRM integration and follow-up logic. #8 
GlockApps Situational Inbox placement testing across Gmail, Outlook, Yahoo, and other providers. #10 
Warmy.io Niche Mailbox warmup with deliverability monitoring and spam testing. #11 
Amazon SES Niche Raw email sending infrastructure (SMTP/API) for custom-built outbound systems. #12 
Infraforge Niche Automated domain and mailbox provisioning for cold email infrastructure. Learning guide
Setup
Connect new mailboxes to Warmup Inbox before connecting them to your sending platform. The platform automatically sends emails to other users in the warmup network, simulating opens and replies. No manual configuration required; warmup starts immediately.
First thing to build
After connecting mailboxes, monitor warmup progress in the dashboard (emails sent, replies received, warmup score). Wait 2-3 weeks until the warmup score is high (above 80), then connect the mailbox to your sending platform and launch campaigns.
What actually matters
- Warmup duration: 2-3 weeks minimum before using mailboxes for cold email campaigns
- Network engagement: Warmup Inbox sends emails to other users and simulates realistic engagement automatically
- Cost: cheaper than Mailreach, suitable for warming many mailboxes on a budget
- No tuning: warmup cadence and reply behavior are automatic and not configurable
Watch out
No inbox placement testing means you will not know if warmup succeeded until you start sending real campaigns.