The Audit Offer at Volume, Run Through Instantly
There are two ways for an SEO agency to run audit-led outbound. The artisanal version — a hand-built teardown per prospect — converts well but caps out at a few hundred prospects a month before the research time eats the margin. The volume version is different: one sharp, specific observation per vertical, written once and sent to every prospect in that segment, with Instantly's campaign engine keeping a thousand-plus prospects in sequence at all times.
Instantly is built for exactly that second motion — fast campaign setup, A/Z variant testing, and the Unibox to handle replies at scale. What it doesn't provide is the sending infrastructure underneath. That's ColdRelay: the secondary domains, mailboxes, and dedicated IPs your Instantly campaigns actually send from. This guide covers the full volume play — provisioning capacity on ColdRelay, bulk-importing it into Instantly, and structuring vertical-segmented campaigns that keep the pipeline full without per-prospect research.
Why Run Instantly on ColdRelay Infrastructure
Instantly's paid plans famously allow unlimited email accounts — the platform is designed for agencies that connect dozens or hundreds of mailboxes and rotate sends across them. But Instantly doesn't provision those mailboxes; it sends from whatever you connect. The 'unlimited accounts' promise is only as good as the infrastructure you plug into it.
That's where ColdRelay fits. You provision mailboxes on isolated Azure tenants with dedicated IPs, fully DNS-configured (SPF, DKIM, DMARC) and ready in about an hour. There's no warmup waiting period before sending — warmup runs continuously as part of each mailbox's 4 sends/day budget (2 outbound + 2 warmup). With 100-150 mailboxes supported per domain, a single ColdRelay order can fill out the sending capacity a volume campaign needs.
The pairing is additive, not competitive: Instantly is the sending and sequencing layer — campaigns, variant testing, Unibox, analytics. ColdRelay is the infrastructure layer underneath. You keep everything that makes Instantly fast to operate, and you feed it mailboxes built to land at 95%+ inbox placement.
Visit Instantly →Connecting ColdRelay Mailboxes to Instantly
Size the mailbox order from your monthly prospect target
Start from the number, not the gut. To keep 1,000+ prospects/month entering sequence with a 4-step cadence, you need roughly 4,000+ sends/month — about 135 outbound sends per working day. At 2 outbound sends/day per mailbox (each mailbox's budget is 4 sends/day total, split 2 outbound + 2 warmup), that's about 70 mailboxes. Order 70-100 on ColdRelay across one secondary domain — ColdRelay supports 100-150 mailboxes per domain — and everything provisions on isolated Azure tenants with dedicated IPs in about an hour.
Bulk-import the mailboxes into Instantly via CSV
Export your mailbox list with SMTP/IMAP credentials from the ColdRelay dashboard. In Instantly, go to Email Accounts → Add New → Bulk Import via CSV and upload the file. Instantly connects every mailbox in one pass — no per-account setup — which is the whole point of pairing a bulk infrastructure order with a platform built for unlimited accounts.
Cap daily sending limits to match the ColdRelay budget
Set each account's daily campaign limit in Instantly to 2 emails. That mirrors the ColdRelay per-mailbox budget of 4 sends/day total — 2 outbound + 2 warmup. Leave Instantly's own warmup toggled off for these accounts; ColdRelay's warmup already runs continuously, and stacking a second warmup layer spends budget without improving placement.
Build one campaign per vertical with A/Z opener variants
In Instantly's campaign builder, create a separate campaign for each vertical you target — e-commerce, B2B SaaS, local services — each with its own vertical-level audit hook written once for the whole segment. Then load A/Z variants of the first email: an audit-led opener (the observation) against a results-led opener (the outcome you got a similar company). Instantly splits sends across variants automatically and reports which one books calls.
Attach the mailbox pool, launch, and staff the Unibox
Add all imported ColdRelay accounts to each campaign and let Instantly rotate sends across the pool. Replies from every mailbox land in the Unibox — one queue, regardless of which of your 70+ addresses the prospect answered. At volume, the Unibox is where the offer actually converts; treat it as a daily staffed inbox, not a notification feed.
The SEO Agency Instantly Playbook
Write the audit hook per vertical, not per prospect
The scalable version of the audit opener is one researched observation that's true across a segment: 'most Shopify stores we audit lose 20-40% of category-page traffic to collection-page cannibalization' lands with every e-commerce prospect, no per-domain research required. One hour of segment research replaces hundreds of hours of prospect research — and because each Instantly campaign maps to one vertical, the hook stays specific without ever being manual.
Settle the audit-vs-results question with A/Z data, not opinion
Every agency debates whether to open with the problem ('here's what's likely broken') or the proof ('here's what we did for a company like you'). Stop debating: run both as A/Z variants in the same Instantly campaign and let 500 sends per variant decide. Verticals answer differently — local-service owners tend to reward results-led openers, in-house SEO leads tend to reward audit-led ones — so test per campaign rather than copying a winner across segments.
Plan capacity so the sequence never goes hungry
Volume outbound fails quietly when list-building lags sending: campaigns drain, mailboxes idle, and the month's capacity is gone. Work the math backwards — 70 mailboxes at 2 outbound sends/day is roughly 3,000 sends/month, which supports about 1,000 new prospects/month on a 3-step sequence. Hold a standing weekly quota of 250 net-new verified prospects per vertical, and when list-building consistently outruns sending, add mailboxes on ColdRelay before throttling the list.
Read campaign analytics by vertical, kill the laggards
Because each vertical runs as its own Instantly campaign, the analytics dashboard becomes a portfolio view: reply rate and positive-reply rate per segment, side by side. Review it weekly and reallocate ruthlessly — pause the vertical pulling 1% replies, shift its mailbox allocation to the one pulling 5%, and draft a fresh hook for the paused segment before relaunching. At volume, segment selection moves pipeline more than copy polish does.
Typical SEO Agency Volume Benchmarks (Instantly + ColdRelay)
| Metric | Benchmark | Notes |
|---|---|---|
| Inbox placement rate | 95%+ | Dedicated IPs and isolated tenants outperform shared Google/Microsoft pools |
| Reply rate | 2-5% | Vertical-level hooks trade a little reply rate for 5-10x the volume of per-prospect audits |
| New prospects entering sequence per month | 1,000+ | Sustained with 70-100 mailboxes and a standing weekly list-building quota |
| Outbound capacity per mailbox | 2/day | 4 sends/day total per mailbox — 2 outbound + 2 warmup |
| A/Z opener test resolution time | 2-3 weeks | ~500 sends per variant gives a readable winner at volume sending rates |
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 at the 70-100+ mailbox counts a volume motion runs. DNS, dedicated IPs, and isolated Azure tenants are included.
Instantly is billed separately on its own subscription for campaigns, A/Z testing, the Unibox, and analytics — paid plans allow unlimited connected email accounts, priced per its current plans.
Because Instantly doesn't charge per connected account, your cost of scale lives almost entirely on the infrastructure side — mailbox count is the dial. That makes capacity planning simple: pick a monthly prospect target, derive the mailbox count, and both bills are predictable from there.
| 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, not competitors. Instantly handles campaigns, sequencing, A/Z variant testing, the Unibox, and analytics. ColdRelay provides the underlying domains, mailboxes, and dedicated IPs that Instantly sends from. You use them together: infrastructure below, sending software on top.
How many mailboxes do I need to keep 1,000+ prospects a month in sequence?
Roughly 70-100. A 1,000-prospect month on a 3-4 step sequence needs about 3,000-4,000 sends. At 2 outbound sends/day per mailbox — each mailbox's budget is 4 sends/day total, split 2 outbound + 2 warmup — 70 mailboxes covers the floor and 100 gives headroom for follow-ups and growth. ColdRelay supports 100-150 mailboxes per domain, so the whole order can sit on a single secondary domain.
Should I turn on Instantly's warmup for ColdRelay mailboxes?
No. ColdRelay mailboxes warm continuously as part of their built-in budget — 2 of each mailbox's 4 daily sends are warmup, alongside 2 outbound. There's no waiting period before you can start campaigns, and running Instantly's warmup on top would double-warm without improving placement. Point Instantly at outbound sending only.
Do vertical-level hooks actually work, or do I need per-prospect personalization?
Both work — they're different motions. Per-prospect audits convert better per send but cap your volume at whatever your research time allows. A vertical-level hook (one specific, true observation per segment) typically pulls 2-5% replies instead of 3-7%, but lets you run 5-10x the prospects through Instantly with the same team. Most agencies running the volume play reserve per-prospect research for warm replies, where the audit effort is spent on someone who already raised a hand.