From Signed Req to Candidate Inboxes in 24 Hours
The hardest moment in staffing isn't winning the client — it's the Monday morning a client opens 40 seasonal seats and expects submittals by Friday. The firms that win those contracts again next season are the ones whose candidate outreach is in-flight by Tuesday, not the ones still spinning up sending capacity on Wednesday.
That reactive motion is what this guide is about. Instantly is the sending layer — the campaign builder, A/Z testing, and Unibox where your candidate outreach actually runs. ColdRelay is the infrastructure underneath it: the secondary domains, mailboxes, and dedicated IPs that are already warm and waiting when the req drops. Wire the two together correctly and speed-to-fill stops depending on how fast you can provision email.
Why Run Instantly on ColdRelay Infrastructure
Instantly is built for exactly this kind of fast-launch sending: a simple campaign builder, bulk SMTP/IMAP import via CSV, and — critically for staffing — unlimited email accounts on paid plans. Connecting your 80th mailbox costs the same in software as connecting your 8th. What Instantly doesn't do is create the mailboxes themselves or guarantee they land; that's the infrastructure layer.
ColdRelay is that layer. Mailboxes provision on isolated Azure tenants with dedicated IPs, DNS (SPF, DKIM, DMARC) pre-configured, live in about an hour — and there's no warmup period before they can send, because warmup runs continuously as part of each mailbox's 4 sends/day budget (2 outbound + 2 warmup). At 100-150 mailboxes per domain, a firm can keep a genuinely large standby pool warm on very few domains.
The two are complementary layers, not competitors: ColdRelay keeps a surge-ready pool of deliverable mailboxes warm; Instantly is the trigger you pull when the req lands. Because Instantly never charges per connected account, your software cost stays flat no matter how big the standby pool gets — surge capacity becomes a pure infrastructure decision.
Visit Instantly →Building a Surge-Ready Instantly Setup on ColdRelay
Provision the pool for your worst Monday, not your average week
Size the ColdRelay pool against the largest req you realistically take — if a client can open 40 seats and you want 2,000 candidates touched in week one, that's roughly 150 mailboxes at 2 outbound sends/day each (4/day total, 2 outbound + 2 warmup). ColdRelay supports 100-150 mailboxes per domain, and the whole pool provisions on isolated Azure tenants with dedicated IPs in about an hour, DNS pre-configured.
Bulk-import every mailbox into Instantly via CSV
Export SMTP/IMAP credentials from the ColdRelay dashboard and use Instantly's bulk CSV import under Email Accounts to connect the entire pool in one pass. Instantly's paid plans include unlimited email accounts, so connecting 150 mailboxes adds zero software cost over connecting 15.
Set sending limits and turn Instantly's warmup off
Cap each account at 2 outbound emails/day in Instantly to match ColdRelay's per-mailbox budget — 4 sends/day total, split 2 outbound + 2 warmup. ColdRelay's warmup runs continuously on its side, including on idle standby mailboxes, so leave Instantly's warmup disabled rather than stacking the two.
Pre-build one campaign template per role family
In Instantly's campaign builder, create a template per role family you place — CDL drivers, warehouse associates, ICU travel nurses, customer-support reps — with merge fields for pay rate, shift, location, and start date. Add A/Z variants on the subject and opening line up front, so every future launch starts with a test already running.
Launch by cloning, then watch Unibox and analytics
When a req drops, clone the matching role-family template, fill the five merge fields, attach the mailbox pool, and launch — minutes of work, not days. Candidate replies flow into Unibox for same-day screening, and Instantly's campaign analytics show within 48 hours which variant is pulling candidates so you can shift volume to it.
The Speed-to-Fill Instantly Playbook
Keep a standby pool that's always warm
The expensive mistake is provisioning after the req arrives. Keep your ColdRelay pool live year-round — warmup runs continuously as part of each mailbox's 4/day budget (2 outbound + 2 warmup), so standby mailboxes stay deliverable even in weeks they send no campaigns. When the req lands, day-one capacity is already there.
Treat role families as products with pre-built campaigns
Most staffing reqs are variations on roles you've filled before. A library of Instantly templates per role family — already A/Z-structured, already merge-fielded — turns campaign creation from a copywriting project into a five-field form. The req-to-first-send clock should be measured in hours.
A/Z test the pay line, not just the subject
Candidates decide on concrete terms. Use Instantly's A/Z variants to test how comp is framed — '$28/hr' vs. '$56K+ annualized' vs. 'top of local market' — per role family and metro. The winning frame differs between a CDL driver in Texas and a travel nurse in Ohio, and Instantly's analytics will tell you which within days.
Measure reply-to-screen time, because candidates expire
An interested candidate is shopping every firm at once and is often gone within 48 hours. Tag Unibox replies by req and route them straight to a screening call the same day — the metric that predicts fill rate isn't reply rate, it's the hours between a candidate's reply and your recruiter's phone screen.
Typical Speed-to-Fill Benchmarks (Instantly + ColdRelay)
| Metric | Benchmark | Notes |
|---|---|---|
| Inbox placement rate | 95%+ | Dedicated IPs and isolated tenants — critical when candidate lists skew toward consumer inboxes |
| Req-to-first-send time | Under 24 hours | Standby pool already warm + cloned role-family template in Instantly |
| Candidate reply rate | 6-12% | Job offers outperform client BD; highest with pay rate and shift stated in the first two lines |
| Outbound capacity per mailbox | 2/day | 4 sends/day total per mailbox — 2 outbound + 2 warmup |
| Time to expand the pool mid-surge | ~60 minutes | New ColdRelay mailboxes need no warmup period and bulk-import into Instantly via CSV |
What It Costs: Instantly + ColdRelay
Billed per mailbox per month, with volume tiers that drop as you scale (see the table below) — a surge-sized standby pool lands in the cheaper tiers fast. DNS, dedicated IPs, and isolated Azure tenants are included, and a warm idle mailbox costs the same whether it sent campaigns this week or not.
Instantly is a separate subscription for campaigns, A/Z testing, Unibox, and analytics — and because paid plans include unlimited email accounts, that subscription doesn't grow when your mailbox pool does.
This combination makes surge capacity flat-cost on the software side: scaling from 50 to 150 mailboxes changes only the per-mailbox infrastructure bill, never the Instantly bill. Capacity planning becomes one variable instead of two.
| 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
Is ColdRelay an alternative to Instantly?
No — they're complementary layers of the same stack. Instantly is the sending software: campaign builder, A/Z testing, Unibox, and analytics. ColdRelay is the infrastructure underneath: the secondary domains, mailboxes, and dedicated IPs Instantly sends from. A staffing firm runs both together — Instantly can't send well without deliverable mailboxes, and ColdRelay mailboxes need a sequencer on top.
Instantly already offers unlimited email accounts — so what am I paying ColdRelay for?
Unlimited accounts means Instantly doesn't charge software fees per connected mailbox — it doesn't mean the mailboxes exist. You still need real domains, mailboxes, dedicated IPs, and DNS, and that's what ColdRelay provides. The pairing is actually why the combo suits surge-driven staffing: your only scaling cost is the per-mailbox infrastructure, while the Instantly subscription stays flat.
A client just opened 40 seats — how fast can we actually start candidate outreach?
If your standby pool is already warm, same day: clone the role-family template in Instantly, fill the merge fields, and launch. If you need more capacity, new ColdRelay mailboxes provision in about an hour with DNS pre-configured and no warmup period before sending — warmup runs continuously as part of the 4 sends/day budget (2 outbound + 2 warmup) — and they bulk-import into Instantly via CSV the same morning.
How many mailboxes do we need to support a 40-seat surge?
Work backward from candidate volume. Filling 40 seats typically means reaching 1,500-2,500 candidates in the first week or two. At 2 outbound sends/day per mailbox (4/day total with 2 warmup), 150 mailboxes deliver 300 first-touches a day — about 2,100 a week — which covers the surge with room for follow-ups. ColdRelay supports 100-150 mailboxes per domain, so that pool fits on one or two secondary domains.