Kit ◆
ConvertKit (now Kit) is an email-first platform that automates email marketing, newsletter growth, and digital product sales for creators.

Warmupinbox (Email Marketing): Warmupinbox is an email warmup tool that builds sender reputation with real inboxes, improving deliverability and inbox placement. Pricing: from $15/inbox/mo. (data verified August 2026)
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Warmupinbox is an automated email warmup tool that improves your sender reputation by connecting your inbox (Gmail, Outlook, Google Workspace, or any SMTP) to a network of 30,000+ real human inboxes. These inboxes open, reply, and mark your emails as not spam, teaching spam filters that your domain is legitimate. This helps land your emails in the Primary inbox instead of Spam.
Cold email senders often struggle with poor deliverability — emails landing in spam or promotions. Warmupinbox solves this by building a positive sender reputation over time, reducing bounce rates and improving inbox placement. It also monitors 100+ blacklists and automatically initiates rescue if you get listed, helping you get delisted faster.
Warmupinbox is ideal for sales teams, marketers, agencies, and recruiters who rely on cold email campaigns. It's also useful for lifecycle teams sending regular emails to customers. It's not designed for transactional email senders or those looking for a full email marketing platform.
Sales teams warm up new domains before outreach; marketers ensure newsletters hit Primary; agencies manage warmup for multiple clients; recruiters improve response rates on cold outreach. With 2x faster warmup than other tools, expect results in as few as 3 days.
Editorial score from our review methodology — not user ratings.
Warmupinbox pricing: from $15/inbox/mo. Billing model: Free.
75 warmup messages/day, replies up to 25%, access to 30K+ inboxes, spam & category monitoring, email reputation check, outreach sequences, dashboards, human-like AI content, developer API, customer support chat, affiliate program.
250 warmup messages/day, replies up to 45%, plus everything in Basic, add your own templates, choose warmup topics, language warmup, custom settings, template statistics, ESP-specific warmup, scheduled warmup, priority support.
1,000 warmup messages/day, replies up to 50%, everything in Pro, premium support, technical setup check, unlimited API, early access to new features.
For 15+ inboxes, volume discounts past 50, multi-client workspaces, white-label reports, and consolidated billing.
All plans come with a 7-day free trial, no credit card required.
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