Available on all CallSine plans once cold email domains & inboxes have been purchased.
Overview
Cold Email Infrastructure (CEI) is the system CallSine uses to send outbound email at scale while protecting your sender reputation.
It runs automatically in the background—so you can focus on messaging, targeting, and campaign strategy while CallSine manages deliverability.
You’ll interact with CEI when setting up new domains or adding inboxes. For setup steps, see the articles on setting up cold email domains and inboxes and reading the Cold Email Infrastructure table.
How It Works
Dedicated Domains and Inboxes
CallSine uses secondary domains that closely resemble your main business domain.
Each secondary domain includes dedicated inboxes used only for cold outreach.
This separation protects your primary domain from any deliverability risks.
When you create new inboxes, they automatically appear in the Cold Email Infrastructure table under their associated domain.
Domain Warming
Before an inbox begins sending outreach, CallSine runs a four-week Warmup period.
During Warmup, each inbox automatically sends and receives low-volume, realistic emails to establish trust with providers and build a positive sending reputation.
After Warmup completes, the inbox status changes to Ready, and it becomes available for Agents to use in campaigns.
Warmup is mandatory for all new inboxes and cannot be skipped or accelerated.
Smart Email Distribution
When multiple inboxes are available, CallSine automatically balances sending volume across all active inboxes.
This ensures consistent delivery patterns and prevents any single inbox from being overused.
Distribution happens automatically—you don’t need to assign prospects manually.
Inbox usage and performance metrics are visible in Analytics.
Inboxes that reach their daily send limit pause automatically until the next send window.
Deliverability Safeguards
CEI applies deliverability best practices behind the scenes to keep sending reliable and compliant.
These safeguards include:
Daily send limits (up to 20 emails per inbox)
Automatic bounce and spam monitoring
Even message distribution across domains
Progressive ramp-up during Warmup to protect reputation
The Agent will not accelerate sending in ways that violate deliverability rules.
Scaling Outreach
Each cold email inbox can safely send up to 20 emails per day.
To increase your total sending volume, add more inboxes under your Cold Email Infrastructure.
CallSine will handle all domain setup, validation, Warmup, and message distribution automatically.