ColdStackColdStack.co
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Related Products
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About
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.
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About
SubsiMail is a self-hosted cold email sequencing platform. Prospect lists, templates, connected inboxes, and all campaign data live in your own database, not a third-party SaaS. It's built as a self-hosted alternative to Instantly, Smartlead, lemlist, and Apollo, with flat per-inbox pricing instead of per-seat fees, full data ownership and export, no content review, and no third-party access to your contacts or campaigns. Runs as a single Docker container on any $5 VPS. Connect Gmail, Outlook, or any SMTP/IMAP inbox; build multi-step sequences with merge fields and reply detection; manage per-user roles (admin/manager/view-only) with a full audit trail; and integrate via a REST API with personal API keys. The first connected mailbox is free forever.
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Platforms Supported
Windows
Not Supported
Mac
Not Supported
Linux
Not Supported
Cloud
Supported
On-Premises
Not Supported
iPhone
Not Supported
iPad
Not Supported
Android
Not Supported
Chromebook
Not Supported
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Platforms Supported
Windows
Not Supported
Mac
Not Supported
Linux
Supported
Cloud
Not Supported
On-Premises
Supported
iPhone
Not Supported
iPad
Not Supported
Android
Not Supported
Chromebook
Not Supported
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Audience
B2B companies
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Audience
Sales teams, agencies, recruiters, and solo founders running cold email outreach who want to own their data instead of trusting a third-party SaaS with their prospect lists.
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Support
Phone Support
Not Supported
24/7 Live Support
Not Supported
Online
Not Supported
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Support
Phone Support
Not Supported
24/7 Live Support
Not Supported
Online
Supported
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API
Offers API
Not Supported
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API
Offers API
Not Supported
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Screenshots and VideosNo images available
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Screenshots and VideosNo images available
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Pricing
No information available.
Free Version
Not Supported
Free Trial
Not Supported
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Pricing
Free (paid plans from $49/mo)
Free Version
Supported
Free Trial
Not Supported
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Reviews/
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Reviews/
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Training
Documentation
Not Supported
Webinars
Not Supported
Live Online
Not Supported
In Person
Not Supported
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Training
Documentation
Supported
Webinars
Not Supported
Live Online
Not Supported
In Person
Not Supported
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Company InformationColdStack.co
Founded: 2025
United States
www.coldstack.so/
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Company InformationSubsiMail
Founded: 2026
India
subsimail.com
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Categories |
Categories |
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Integrations
Gmail
Supported
Microsoft Outlook
Not Supported
Slack
Supported
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Integrations
Gmail
Supported
Microsoft Outlook
Supported
Slack
Not Supported
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