Introduction to Zylar
What Zylar is and how its core concepts fit together, from workspaces, domains and inboxes to warm-up, sequences, leads and the Unibox for replies.
Zylar is a cold email sequencer built by cold emailers, with AI on every layer. It runs your sequences and also takes on the infrastructure work behind them: domain DNS checks, warm-up, inbox rotation and deliverability monitoring. This page explains what Zylar does and how its core concepts relate, so the rest of the docs make sense.
What Zylar handles for you
Cold email fails most often because of infrastructure, not copy. Zylar runs four deliverability layers by default on every workspace:
| Layer | What Zylar does |
|---|---|
| Setup | Checks SPF, DKIM, DMARC, a custom tracking domain and MX the moment you connect a domain, and tells you exactly what to fix with the record to paste. |
| Warm-up | Warms every inbox through a private pool of real inboxes, with opens, replies and "not spam" marks on a ramp schedule. |
| Sending | Rotates each campaign across inboxes, with daily caps, random gaps and time-zone sending windows. |
| Monitoring | Runs placement tests per domain for Gmail and Outlook and scores every inbox's health daily. Domains that drop below your threshold auto-pause. |
On top of that, AI writes copy, answers replies, runs follow-ups and A/B tests variants for you.
Core concepts
Workspaces
A workspace is the top-level container. Each workspace holds its own domains, inboxes, sequences, leads and replies, isolated from every other workspace. Agencies typically create one workspace per client. Workspaces and teammates are unlimited, and API keys are scoped to a single workspace. See Workspaces and roles.
Domains
A domain is a sending domain you connect to a workspace. When you connect it, Zylar checks its DNS records (SPF, DKIM, DMARC, custom tracking domain and MX). Placement tests and auto-pause also work at the domain level. See Connect a domain.
Inboxes
An inbox is a mailbox on one of your domains that sends email. You can connect Gmail, Outlook or any SMTP/IMAP inbox, one at a time or in bulk. Each inbox has a daily limit, a health score from 0 to 100 updated daily, and a status: active, warming or resting. Inboxes are unlimited on every plan.
Warm-up
Warm-up builds and maintains each inbox's sending reputation. It starts when you connect an inbox, ramps until the inbox is ready for cold sends. How long depends on the inbox type: about 10–14 days for Outlook tenants (3–7 days minimum), 15–25 days for Google Workspace and 4–6 weeks for private SMTP, is free on every plan and never counts toward your monthly sends. Zylar also puts inboxes and domains back on warm-up when their health drops. See Warm-up.
Sequences
A sequence is a multi-step cold email campaign: up to 10 steps with delays, personalization, spintax and A/B/C variants. Zylar spreads each sequence across your inboxes and stops it for a lead the moment that lead replies, bounces or unsubscribes. See Sequences.
Leads
A lead is a contact you add to a sequence. Each lead has an email address and optional fields such as first name, last name, company and custom fields, plus a status such as active, replied or interested. Verification and enrichment credits are included on every plan. See Leads.
Unibox
The Unibox is one inbox for replies across every mailbox and every client. Replies are labelled by intent (for example Interested, Not now or OOO), and you can reply, assign the lead to a teammate or push it to HubSpot from there. See Unibox.
How the pieces relate
- A workspace contains one or more domains.
- Each domain has one or more inboxes, which warm up before and while they send.
- A sequence sends to leads by rotating across healthy inboxes.
- Replies from every inbox land in the Unibox, where they're labelled and handled.
- Monitoring watches domains and inboxes the whole time, pausing or resting anything that starts to slip.
Everything above is also available programmatically through the REST API, webhooks and the MCP server.
Next steps
- Follow the Quickstart to go from a connected domain to a live sequence.
- Read about the deliverability layers in more depth.
- Compare plans.