Stop Missing Positive Replies
Connect Instantly, Smartlead, and EmailBison directly to your Slack workspace. Reply to leads without leaving Slack.
Loved by 73+ agencies
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Mobile ready. Hubspot & Salesforce sync coming soon.
Your Cold Emails Are BLEEDING Revenue
Book a 15-min audit. We'll review:
Infrastructure · Deliverability · Copy · Lists · Reply management
Then show you exactly where you're losing $20K-$50K/month.
We've audited 50+ setups and found leaks in every single one
The #1 Unibox for Cold Email Outreach
Whether you manage one campaign or hundreds, Coldstack helps you stay on top of every reply without leaving Slack.
Connect Your Sender
Link your Instantly, Smartlead, or EmailBison accounts to Coldstack in seconds. No complex setup required.
Receive Replies in Slack
All positive replies from your campaigns automatically flow into a dedicated Slack channel. Never miss a hot lead again.
Reply Instantly from Slack
Click reply directly in Slack and your response goes straight to the lead. No need to log into multiple platforms.
Close Deals 3x Faster
Respond to warm leads in minutes, not hours. Your team stays in Slack while booking more meetings than ever.
Simple, transparent pricing
Choose your plan. All plans include unlimited team members and real-time notifications.
Solo
Perfect for individuals and small teams getting started with Slack-native outreach.
Get Started Free14-day free trial · No CC Required
Agency
For agencies managing multiple client accounts with full whitelabel capabilities.
Get Started Free14-day free trial · No CC Required
Frequently Asked Questions
Everything you need to know about Coldstack
Your Cold Emails Are BLEEDING Revenue
Book a 15-min audit. We'll review:
Infrastructure · Deliverability · Copy · Lists · Reply management
Then show you exactly where you're losing $20K-$50K/month.
We've audited 50+ setups and found issues in every one