
lemlist
Instantly.ai
Apollo.io
Reply.io
Mailshake
Hunter.io
SmartLead.ai
Snov.io
InboxStack
GlockApps
Email Testing By Inbox Pirates
Validity LLC
MxToolBox
Folderly
HetrixTools
Inbox AI
lemlist is the #1-ranked sales engagement platform on G2, used by 20,000+ B2B companies to run multichannel outbound at scale. It covers the full outbound workflow in a single tool: a 600M+ contact database, waterfall enrichment (80% email find rate across 8 providers), multichannel sequences (email, LinkedIn, WhatsApp, phone), AI-powered personalization, a complete deliverability stack, unified inbox, and native CRM integrations with HubSpot, Salesforce, and Pipedrive. Founded in 2018, bootstrapped to $50M ARR and profitable.
InboxStack is an email deliverability intelligence platform built for teams who need to know why their emails aren't reaching the inbox โ not just that they aren't. At its core is Brain, a proprietary causal AI engine trained on a 22-year deliverability knowledge base, which correlates signals across your ESP, DNS authentication records (SPF, DKIM, DMARC), Google Postmaster Tools, Microsoft SNDS, and 50+ blocklists to pinpoint root causes instead of surfacing raw metrics.
Most deliverability tools stop at monitoring: they show you a drop in inbox placement or a blocklist hit and leave you to investigate. InboxStack goes further, tracing the actual causal chain โ a DKIM misalignment, a reputation dip on a specific sending IP, a content trigger โ so you can fix the real problem instead of guessing.
Setup takes minutes with no migration required: forward your email headers for an instant DNS/authentication audit, or connect your existing ESP and Postmaster accounts for ongoing monitoring. Optional seed testing gives you real inbox-vs-spam placement data across major providers.
Built for agencies managing multiple client domains and growing companies who've outgrown basic authentication checkers, InboxStack turns deliverability from a black box into a diagnosable, fixable system.
lemlist
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Instantly.ai - Build your own infinitely scalable cold email outreach system with Instantly.
GlockApps - G-Lock Apps is an interesting tool that might seem simple to some, but is quite essential to most online marketers.
Apollo.io - Apolloโs predictive prospecting, sales engagement, and actionable analytics help the teams to reach its full revenue potential.
Email Testing By Inbox Pirates - Preview, Analyze & Test emails with one click.
Reply.io - Reply.io is an AI-driven sales engagement platform that automates cold outreach through unlimited mailboxes, converts website traffic into booked meetings with AI Chat, and empowers your team to streamline the entire sales process with AI SDRs.
Validity LLC - Founded in 2010, located in Essex Countyโs City of Orange, NJ, and serving all 50 states of the U.S., Validity, LLC is considered a โOne Stop Shopโ for ...