Agency Cold Email, Run Through Instantly
For a lead gen agency, cold email isn't a channel — it's the product. You're running outbound for ten, thirty, or a hundred clients at once, and every client expects their campaigns to land, their reporting to be clean, and their results to be isolated from whatever your other clients are doing. Instantly is where that delivery work happens: campaigns, inbox rotation, the Unibox, client workspaces. ColdRelay is the layer underneath — the domains, mailboxes, and dedicated IPs that all those Instantly campaigns actually send from.
This guide covers how agencies wire the two together: provisioning per-client mailbox pools on ColdRelay, bulk-importing them into Instantly, isolating clients from each other, and re-allocating capacity when clients churn — without ever rebuilding infrastructure from scratch.
Why Run Instantly on ColdRelay Infrastructure
Instantly's plans famously include unlimited email accounts — you can connect as many sending mailboxes as you want without per-seat software fees. That's a gift for agencies, but it shifts the real question one layer down: where do hundreds of deliverable mailboxes actually come from? Instantly connects mailboxes; it doesn't provision domains, configure DNS, or give each client their own IP reputation. That's the infrastructure layer's job.
That's where ColdRelay fits. Instead of juggling Google Workspace seats across dozens of client billing accounts, you order mailboxes on isolated Azure tenants with dedicated IPs — SPF, DKIM, and DMARC pre-configured, ready in about an hour. Each client gets their own domains and their own isolated tenant, so one client's aggressive campaign can never burn another client's reputation. And because the agency owns the infrastructure relationship, a churned client's mailbox pool becomes capacity you re-deploy, not a Workspace account you cancel.
The pairing is additive, not competitive: ColdRelay is the infrastructure, Instantly is the sending engine on top. You keep Instantly's unlimited-account model, campaign rotation, and Unibox — you just feed it mailboxes built to land.
Visit Instantly →Connecting ColdRelay Mailboxes to Instantly, Client by Client
Provision a per-client mailbox pool on ColdRelay
For each client, order secondary domains that echo the client's brand (not yours, and never their primary domain). ColdRelay supports 100-150 mailboxes per domain, so a typical client pool of 30-100 mailboxes fits on one or two domains. Everything provisions on isolated Azure tenants with dedicated IPs in about an hour, DNS (SPF, DKIM, DMARC) already configured — fast enough to onboard a client the same day they sign.
Export credentials for bulk import
From the ColdRelay dashboard, export the client's mailbox list with SMTP/IMAP credentials as CSV. The column layout matches what Instantly's bulk importer expects, so a 100-mailbox client pool is one upload, not a hundred manual connections.
Bulk-import into the client's Instantly workspace
In Instantly, open (or create) the client's workspace, then go to Email Accounts → Add New → Bulk Import via SMTP/IMAP and upload the CSV. Keeping one workspace per client keeps accounts, campaigns, and Unibox replies cleanly separated — and makes white-label client reporting trivial.
Set sending limits to match the ColdRelay budget
Set each mailbox's daily campaign limit in Instantly to 2 outbound emails per day. That mirrors ColdRelay's per-mailbox budget — 4 sends/day total, split 2 outbound + 2 warmup. Warmup runs continuously on ColdRelay's side as part of that budget, so there's no separate warmup period before campaigns can start and no need to double-warm inside Instantly.
Attach the pool to campaigns and let rotation work
Build the client's campaign in Instantly, attach every mailbox in their pool, and let Instantly's inbox rotation spread sends evenly across accounts. A 50-mailbox client pool gives you 100 outbound sends/day for that client; when they want more volume, you add mailboxes on ColdRelay and re-import — the campaign doesn't change.
The Lead Gen Agency Instantly Playbook
Isolate every client at the infrastructure level
Workspace separation in Instantly keeps campaigns organized, but real isolation lives lower: give each client their own ColdRelay domains, dedicated IPs, and isolated Azure tenant. If one client's list quality tanks their reputation, the blast radius is their pool — not your whole book of business.
Treat mailbox pools as re-deployable capacity
Client churn is a fact of agency life. When a client leaves, their domains age out but the capacity lesson stays: provision new pools per client rather than recycling a churned client's domains onto a new account. Fresh domains on a new isolated tenant cost about an hour to stand up — cheaper than explaining inherited reputation to a new client.
Quote retainers against sending math, not vibes
At 2 outbound sends/day per mailbox, capacity is arithmetic: a client paying for ~3,000 emails/month needs roughly 50 mailboxes. Price your retainers from that math, mark up the infrastructure as a line item or bundle it, and scale the pool — not the promise — when clients want more.
Staff the Unibox like it's the product
Clients don't pay for sends; they pay for qualified conversations delivered. Instantly's Unibox aggregates replies across every campaign in a workspace — staff it daily per client, tag positive replies fast, and route them into the client's CRM or a shared sheet. Same-day reply handling is the difference between a 6-month retainer and a 3-month one.
Typical Agency Benchmarks (Instantly + ColdRelay)
| Metric | Benchmark | Notes |
|---|---|---|
| Inbox placement rate | 95%+ | Dedicated IPs and per-client isolated tenants outperform shared Google/Microsoft pools |
| Reply rate | 2-6% | Varies widely by client vertical and list quality; agencies should benchmark per client, not per book |
| Outbound capacity per mailbox | 2/day | 4 sends/day total per mailbox — 2 outbound + 2 warmup |
| Time to onboard a new client's infrastructure | Same day | ~60 minutes to provision the pool on ColdRelay, plus bulk import and campaign setup in Instantly |
| Cost per qualified lead delivered | $30-80 | Blended across infrastructure, software, and labor; tightens as mailbox volume tiers kick in |
What It Costs: Instantly + ColdRelay
You pay per mailbox per month for the infrastructure, with volume tiers that drop as you scale (see the table below) — which matters for agencies, since a multi-client book pushes you into the cheaper tiers fast. DNS, dedicated IPs, and isolated Azure tenants are included.
Instantly is billed separately on its own subscription. Its unlimited-email-account model means connecting more ColdRelay mailboxes doesn't raise your Instantly bill — you pay Instantly for sending volume and features, per its current plans.
Infrastructure cost scales with total mailbox count across all clients; Instantly's cost scales with plan tier, not account count. For agencies that resell capacity, that combination makes per-client margins predictable: one infrastructure bill that gets cheaper per mailbox as you grow, one software bill that stays flat as you connect more accounts.
| Mailboxes | ColdRelay price / mailbox / month |
|---|---|
| 1–199 | $1.00 |
| 200–999 | $0.85 |
| 1,000–4,999 | $0.70 |
| 5,000+ | $0.55 |
Each mailbox sends 4 emails per day — 2 outbound to prospects + 2 warmup. ColdRelay provisions mailboxes on isolated Azure tenants with dedicated IPs; Instantly handles the sending, sequencing, and inbox rotation on top.
Frequently Asked Questions
Does ColdRelay replace Instantly?
No — they're complementary layers. Instantly handles campaigns, inbox rotation, the Unibox, and client workspaces. ColdRelay provides the underlying domains, mailboxes, and dedicated IPs that Instantly sends from. Agencies use them together: ColdRelay for the infrastructure, Instantly for the sending.
How do I keep clients from affecting each other's deliverability?
Provision each client their own ColdRelay pool — separate domains, dedicated IPs, and an isolated Azure tenant per client. Pair that with one Instantly workspace per client. If one client's campaign draws spam complaints, the damage is contained to their own infrastructure and never touches another client's sending reputation or your agency domain.
What happens to a client's mailboxes when they churn?
The agency owns the ColdRelay relationship, so churn is a re-allocation decision, not a fire drill. Most agencies retire the churned client's domains and provision a fresh pool for the next client — new domains on a new isolated tenant take about an hour to stand up, and a new client gets reputation they fully own rather than something inherited.
Instantly includes warmup — do I still need ColdRelay's?
ColdRelay mailboxes run their own continuous warmup — 2 warmup sends/day per mailbox as part of the 4/day budget (2 outbound + 2 warmup) — with no waiting period before campaigns can start. You generally shouldn't double-warm the same mailbox inside Instantly; point Instantly's campaign limits at the 2 outbound sends and let ColdRelay handle warmup underneath.