ColdStack

ColdStack

ColdStack.co
+
+

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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.

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.

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Audience

B2B companies

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.

Support

Phone Support
24/7 Live Support
Online

Support

Phone Support
24/7 Live Support
Online

API

Offers API

API

Offers API

Screenshots and Videos

No images available

Screenshots and Videos

No images available

Pricing

No information available.
Free Version
Free Trial

Pricing

Free (paid plans from $49/mo)
Free Version
Free Trial

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

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Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Training

Documentation
Webinars
Live Online
In Person

Training

Documentation
Webinars
Live Online
In Person

Company Information

ColdStack.co
Founded: 2025
United States
www.coldstack.so/

Company Information

SubsiMail
Founded: 2026
India
subsimail.com

Alternatives

Alternatives

PrimaryHub

PrimaryHub

Voltic
Rubedo

Rubedo

Rubedo.ai

Categories

Categories

Integrations

Gmail
Microsoft Outlook
Slack

Integrations

Gmail
Microsoft Outlook
Slack
Claim ColdStack and update features and information
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