The best cold email software
The Harp team ·
We build Harp, which is on this list, so weigh our take accordingly. Every other tool is described from its own website as of the date above.
Volume infrastructure
- Instantly. Unlimited email accounts and warmup, a 450M+ lead database and AI agents. Best for: high-volume cold email.
- Smartlead. Unlimited mailboxes at no extra cost, AI warmups and a master inbox. Best for: email infrastructure on a low monthly plan.
- Salesforge. Unlimited mailboxes with warm-up, LinkedIn senders and an optional AI SDR. Best for: email plus LinkedIn senders.
Platforms with built-in data
- lemlist. A 650M+ lead database with email, LinkedIn, calls, WhatsApp and SMS. Best for: data and many channels in one tool.
- Apollo. Contact data with sequences and a dialer. Best for: teams already on Apollo’s data.
- Clay Sequencer. Sends from your own Gmail or Outlook or inboxes bought in Clay, and stops on a reply. Best for: teams building lists in Clay.
Researched, agent-run outreach
- Harp (harpgtm.com). The MCP harness for pipeline generation: your agent researches and qualifies with evidence, Harp runs email and LinkedIn sequences, sends from your own mailbox and wakes the agent to answer replies. LinkedIn runs from your real Chrome on your Mac. Runs locally next to Claude Code, Claude Desktop or Cowork. Best for: people whose own agent should run outbound end to end.
Whatever you pick
Use a separate domain, warm every new mailbox, space your sends, include a plain-text version, think twice about tracking and support one-click unsubscribe. Cold email deliverability for agent-run outbound covers each one.
Questions
Is more volume better in cold email?
Only up to what your domains and mailboxes can sustain. Researched emails to fewer, qualified accounts usually protect deliverability better than volume.