Audience
B2B companies
About ColdStack
Stop losing deals in the 2-hour window between lead reply and your response. ColdStack brings every cold email reply from Instantly, Smartlead, and EmailBison into a single Slack channel where your team can see and act instantly.
Each reply triggers a real-time notification with full engagement context—who opened what, when, and how many times. Your team replies directly from Slack, and ColdStack syncs everything back bidirectionally to your source platform. No more toggling between dashboards, Gmail, and Slack.
Built for cold email agencies and sales teams who live in Slack. Mobile-ready through Slack's app.
Other Popular Alternatives & Related Software
InboxKit
InboxKit is the leading cold email infrastructure platform that automates domain and mailbox provisioning at scale. We help cold email agencies, sales teams, and outbound consultancies set up Google Workspace and Microsoft 365 mailboxes in minutes, not hours. Key features include automated DNS configuration, one-click export to 15+ sequencers (Instantly, SmartLead, Lemlist, Reply.io, etc.), real-time deliverability monitoring, and bulk mailbox management. As an official Google Cloud Partner and Microsoft Partner, we provide enterprise-grade infrastructure without the manual setup overhead.
Learn more
lemlist
Personalize cold emails, automate follow-ups, and engage with leads across all channels. lemlist is your sales automation and cold email software in one. From teams of 2 to 200+, lemlist solves every outreach automation challenge. Increase your reply rates by communicating with every prospect on a 1-on-1 level. Write custom intro lines and call-to-actions. Automatically put any screenshot, custom text, or company logos onto images in your emails. Add dynamic landing pages and embed videos. Launch powerful cold email sequences, send follow-ups that don't feel generic, and open more opportunities for your business. Close more deals by engaging with your leads across multiple channels on autopilot. Add cold calls and dial prospects with one click. Include custom tasks and social selling. Sync seamlessly with your team and quickly see at what stage a specific lead is in.
Learn more
Rubedo
Find and pull data such as email addresses, name and phone number from social media platforms and websites. Download unlimited leads ready for prospecting. It is easy. Download the Chrome Extension, and let the tool automate the work for you. Make your customers sending newsletters or cold emails (send emails until recipients reply) by adding their own SMTP provider and IMAP. Track opens, clicks, bounce, unsubscribe, replies and create nice emailing campaigns in plain text or HTML. Convert your visitors into leads. Automatically chat with your visitors and capture data from them. The collected leads information could be sent by email, SMS (mobile number), or directly into a Slack channel. Convert your visitors into leads. Automatically chat with your visitors and capture data from them. You will be able to install a chatbot to capture information from your visitors.
Learn more
Smartlead.ai
Smartlead.ai is a sales email automation platform. It can scale your cold emailing with unlimited mailboxes and AI warmups so you always land in your lead's inboxes. You can use unlimited auto-rotating email accounts and AI-optimized sending to boost reply rates. Its multi-channel outreach feature can also scale your outreach across SMS, LinkedIn, Twitter, WhatsApp, and more.
Learn more
Integrations
Company Information
ColdStack.co
Founded: 2025
United States
www.coldstack.so/
Videos and Screen Captures
Other Useful Business Software
Assembled is the only unified platform for staffing and managing your human and AI support team.
Assembled is the only platform that unifies AI agents and intelligent workforce management to power fast and flexible support operations. Built for scale, we help teams automate over 50% of customer interactions, forecast with 90%+ accuracy, and optimize staffing across in-house and BPO teams. Orchestrate every chat, email, or call, balancing workloads between human and AI agents in real time — without sacrificing quality or control. Trusted by Stripe, Canva, and Robinhood, Assembled transforms support from a cost center into a strategic advantage. Our Workforce and Vendor Management tools connect forecasting, scheduling, and performance for smarter staffing decisions. AI Agents automate conversations across channels with your workflows and brand voice. AI Copilot empowers agents with real-time guidance, suggested replies, and one-click actions for faster, higher-quality resolutions.
Product Details
Platforms Supported
Cloud
