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The complete B2B outreach stack for 2026: four layers, exact tool picks, how Quarvio, Inframail, Instantly, and Aimfox work together in a single system.
James Whitfield
Lead gen agency owner, 50+ campaigns/month · Updated June 24, 2026
Last updated: June 2026 · James Whitfield, lead gen agency owner, 50+ campaigns/month
TL;DR — 7 things to know before reading
A B2B outreach stack is not a collection of tools. It is a system with four interdependent layers where data produced in one layer becomes the input for the next. Contact data sourced in Layer 1 is imported to infrastructure in Layer 2, sent via sequences in Layer 3, and augmented by LinkedIn touchpoints in Layer 4. If any layer is missing, the system breaks at that point.
Most outbound teams build their stack backwards: they start with a sending tool, realise they need infrastructure, add inboxes, and then wonder why contacts are not converting. The correct build order is infrastructure first, then contact data, then sequences, then LinkedIn. This guide covers the four layers in build order and explains exactly how data flows between them.
The unique angle of this guide is the system architecture view. Most stack comparison content lists tools and compares features. This guide covers the exact workflow: how a raw contact record in Quarvio becomes a verified contact in an Instantly campaign via Inframail inboxes, with a parallel LinkedIn touchpoint from Aimfox — and what happens at each handoff point between the layers.
Every outbound system starts with a list of people to reach. The quality of that list determines the ceiling of the entire system. Sophisticated infrastructure and well-written sequences cannot compensate for a low-quality or poorly targeted contact list.
Layer 1 provides verified B2B contact data: name, job title, company, and work email address for each contact. The quality standard for Layer 1 data is:
Quarvio delivers contact data meeting these standards with one-time purchase pricing, no subscription, and credits valid for 12 months. Quarvio-sourced contacts are pre-verified, eliminating the SMTP verification step that unsourced lists require before import.
Step 1.1: ICP definition
Before sourcing any contacts, define the ICP with measurable criteria:
Step 1.2: Contact sourcing
Source a Quarvio contact list matching the ICP definition. The list should be segmented if running multiple ICP variants simultaneously: one list per ICP segment, not one combined list.
Step 1.3: Pre-import audit
Before importing to Layer 3 (Instantly), audit the list:
Layer 1 output: A CSV file with verified contacts, all personalisation fields populated, segmented by campaign.
| Target sends/day | Contacts needed (30-day campaign) | Quarvio package |
|---|---|---|
| 100/day | 3,000 contacts | Starter (5,000 / $129) |
| 300/day | 9,000 contacts | Growth (10,000 / $199) |
| 500/day | 15,000 contacts | Scale (25,000 / $399) |
| 1,000/day | 30,000 contacts | Scale + additional |
| 2,000+/day | 60,000+ contacts | Pro (50,000 / $699) × 2 |
Email infrastructure is the foundation that makes high-volume cold email deliverable. Without dedicated sending infrastructure, cold email lands in spam or triggers provider limits that throttle or block the sending account.
Layer 2 provides:
Inframail provisions Microsoft 365 inboxes with automated DNS setup on dedicated cold email domains. The Microsoft 365 infrastructure provides better inbox placement than Google Workspace for cold email at scale.
Sending cold email from the primary company domain (company.com) risks permanently damaging the domain's reputation. If spam complaints accumulate on the primary domain, all company email — transactional, marketing, and internal — is affected. Cold email domains (company-growth.com, company-outreach.com) isolate cold email reputation from the primary domain.
Per Mailgun's email authentication guide, SPF, DKIM, and DMARC are the three authentication records that email providers use to verify sender identity. All three must be configured on every cold email domain before any production sends.
Step 2.1: Domain provisioning
Purchase cold email sending domains. Naming convention: [brand]-outreach.com, [brand]-growth.com, [brand]-team.com. Use one domain per 2–3 inboxes for reputation isolation.
Step 2.2: Inbox provisioning via Inframail
Provision Microsoft 365 inboxes on each domain via Inframail. Inframail automates DNS record setup (SPF, DKIM, DMARC) eliminating the manual configuration step that is the most common source of deliverability errors in DIY infrastructure setups.
Step 2.3: Warmup via Instantly
Connect all new inboxes to Instantly's warmup system. Warmup mimics real email activity by sending and engaging with emails between warmed inboxes, gradually building the domain's sender reputation with email providers. Warmup timeline per Woodpecker's email warmup guide: 2–4 weeks minimum to production-ready, 8–12 weeks for full reputation maturity.
Step 2.4: Warmup verification
Before launching production sends, verify warmup health via Google Postmaster Tools. Domain reputation must show "High" before any production campaign sends. Sending before High reputation is achieved is the primary cause of early-campaign deliverability failures.
Layer 2 output: Warmed sending inboxes with authenticated domains, connected to Instantly, ready for campaign assignment.
| Target sends/day | Inboxes needed | Domains needed | Monthly Inframail cost |
|---|---|---|---|
| 100/day | 3 inboxes | 2 domains | Low tier |
| 300/day | 7–8 inboxes | 3–4 domains | Mid tier |
| 500/day | 12–13 inboxes | 5–6 domains | Mid tier |
| 1,000/day | 25 inboxes | 10–12 domains | See Inframail pricing |
| 2,000+/day | 50+ inboxes | 20+ domains | Volume tier |
Layer 3 is where contact data and infrastructure combine to produce outreach. Instantly is the campaign management tool that receives contacts from Layer 1, sends through inboxes provisioned in Layer 2, and manages the multi-touch sequence, reply tracking, and inbox rotation.
Step 3.1: Campaign creation
Create one campaign per ICP segment. Do not combine contacts from multiple ICP segments into one campaign — the messaging must be specific to the ICP, which requires separate campaigns.
Step 3.2: Contact import
Upload the Layer 1 Quarvio contact list into the campaign. Instantly deduplicates within a campaign and flags contacts with syntax errors or bounce history.
Step 3.3: Sequence configuration
Build the email sequence:
Configure stop-on-reply (enabled), random delay (3–10 minutes between sends), and daily limit (40–50 per warmed inbox, 20–30 for inboxes under 8 weeks old).
Step 3.4: Sending schedule
Set Monday–Friday, 8:00 AM–5:00 PM in the target timezone. Sends outside business hours have lower open rates and slightly higher spam complaint rates from contacts who expect professional email during working hours.
Step 3.5: Unibox monitoring
Check Unibox daily for Interested and Meeting booked replies. Response time to positive replies must be under 4 hours for optimal conversion to discovery calls.
Layer 3 output: Scheduled campaign running automatically, replies surfaced in Unibox, performance metrics visible in campaign analytics.
| Setting | Recommended value | Location |
|---|---|---|
| Daily send limit per inbox | 40–50 (warmed), 20–30 (new) | Settings → Inboxes |
| Stop on reply | Enabled | Campaign → Sequences |
| Random delay | 3–10 minutes | Campaign → Advanced |
| Sending schedule | Mon–Fri, 8 AM–5 PM | Campaign → Schedule |
| AI reply categorisation | Enabled | Campaign settings |
| Warmup per inbox | Enabled, 4+ weeks before production | Settings → Warmup |
| Inbox rotation | Enabled, auto-distribute | Campaign → Inboxes |
Layer 4 runs in parallel with Layer 3. While Instantly sends email sequences to the Layer 1 contact list, Aimfox runs LinkedIn connection campaigns to the same ICP contacts who have a LinkedIn presence.
Per Woodpecker's multichannel benchmark data, combining email and LinkedIn outreach increases total reply rate by 40–60% versus email alone. This is not because LinkedIn generates more individual replies; it is because the combination creates a multichannel presence that reinforces each channel.
A prospect who receives a cold email and then receives a LinkedIn connection request from the same person (or same company) in the same week sees two independent touchpoints. The combined presence increases recognition, which increases the probability that one of the two channels prompts a response. This effect is strongest for SaaS, agency, and professional services buyers who are active on both email and LinkedIn.
Step 4.1: LinkedIn profile setup
The LinkedIn account used for Aimfox outreach should match the brand and persona of the email sequences. If the email sequences are sent from a specific sender name (e.g., "Alex from Acme"), the LinkedIn account should represent the same persona. Mismatched personas between email and LinkedIn reduce the multichannel reinforcement effect.
Step 4.2: ICP contact matching
Identify which Layer 1 contacts have verified LinkedIn profiles. This is typically 60–80% of ICP contacts for professional roles at companies with 20+ employees. Aimfox runs campaigns targeting LinkedIn users matching the ICP job title and company characteristics.
Step 4.3: Connection campaign configuration
In Aimfox, configure a LinkedIn connection campaign:
Step 4.4: Timing synchronisation with Layer 3
Start the Aimfox LinkedIn campaign on Day 2–3 of the Instantly email sequence. This ensures the LinkedIn touchpoint arrives after the email (reinforcing it) rather than before it (creating a confusing first impression). The email introduces the message; the LinkedIn touchpoint reinforces it.
Layer 4 output: LinkedIn connection requests and follow-up messages running in parallel with email sequences, additional replies surfaced in Aimfox's own inbox management.
Understanding how data moves between layers prevents the most common stack integration errors:
| Data flow | From | To | Format | Common error |
|---|---|---|---|---|
| Contact records | Quarvio (Layer 1) | Instantly (Layer 3) | CSV with name, email, custom fields | Missing personalisation fields cause blank variables in emails |
| Domain credentials | Inframail (Layer 2) | Instantly (Layer 3) | SMTP credentials | Wrong SMTP port or authentication method causes send failures |
| Inbox rotation | Inframail (Layer 2) | Instantly (Layer 3) | Connected inbox pool | Too few inboxes per campaign means daily limits hit quickly |
| Reply notifications | Instantly (Layer 3) | Unibox | Automatic aggregation | Stop-on-reply disabled means automated emails continue after prospect replies |
| LinkedIn contact data | Quarvio ICP (Layer 1) | Aimfox (Layer 4) | LinkedIn search or CSV | ICP mismatch between email list and LinkedIn targeting |
| Timing sync | Instantly sequence day (Layer 3) | Aimfox campaign start (Layer 4) | Manual coordination | LinkedIn touchpoint arriving before email reduces reinforcement effect |
For teams running multiple ICP segments simultaneously, build a complete sub-stack per segment: separate Quarvio list, separate Inframail inboxes, separate Instantly campaign, separate Aimfox campaign. This full isolation prevents reputation cross-contamination between segments and enables independent optimisation of each segment's performance metrics.
Zapier's Instantly integrations enable automated triggers: when a contact moves from Quarvio sourcing to import-ready, a Zapier workflow can auto-import to the correct Instantly campaign. This reduces the manual CSV download/upload cycle that is the most common source of list management errors in multi-segment operations.
Domain reputation accumulates over time. After 6 months of production use, a sending domain's reputation reflects its full send history. If that history includes any spam complaints or bounce spikes, the accumulated reputation debt becomes harder to clear. Rotating to fresh Inframail-provisioned domains every 6 months and maintaining the old domains in warmup produces more consistent long-term deliverability than running the same domains indefinitely.
Contacts who have received Layer 3 email sequences but did not respond become a "warm" tier. These contacts have seen the message and chosen not to engage at that time — they are not permanently unreachable. Create a re-engagement campaign in Instantly that runs 90 days after the original sequence ends, with a different message angle and a different sending inbox. The re-engagement campaign typically shows 30–50% lower reply rates than the original campaign but costs only the contact list credit (already spent) and inbox capacity.
Before running the Aimfox connection campaign, endorse 1–2 skills on the target contact's LinkedIn profile from the sending LinkedIn account. The prospect receives a notification about the endorsement, which creates familiarity before the connection request arrives. The connection request acceptance rate is measurably higher when there is a prior positive interaction on LinkedIn (endorsement, post comment, share) than when the connection request arrives with no prior context.
Symptom: Campaigns show open rates in the 10–15% range even after completing the warmup period.
Cause 1: Warmup was completed on the domain but domain reputation has not yet reached "High" in Google Postmaster Tools. Postmaster reputation lags behind actual warmup progress by 7–10 days. Cause 2: Sending domains share IP addresses with other senders who have accumulated spam reputation. Microsoft 365 inboxes via Inframail use dedicated IP pools, which eliminates shared IP risk. Cause 3: The subject line is triggering spam filters before the email is opened. Subject lines with all-caps words, excessive punctuation, or common spam trigger phrases reduce open rates by 15–25%.
Fix: Check Google Postmaster Tools daily for the affected domain. Wait until domain reputation shows "High" before resuming production sends. Review subject lines against common spam trigger patterns. Reduce daily send volume by 50% for 7 days while reputation stabilises.
Symptom: A prospect replies to say they received both an email and a LinkedIn message with different claims or different sender names.
Cause: Layer 3 and Layer 4 are not synchronised. The email sequence and LinkedIn campaign are running independent messaging without a consistent persona or value proposition.
Fix: Standardise the sender persona across Layer 3 and Layer 4. Use the same name and the same core value proposition in both channels. The LinkedIn message can be shorter and more conversational than the email, but the core claim must match. Review both the Instantly email templates and the Aimfox LinkedIn messages for consistency before launching both simultaneously.
Symptom: Unibox shows a 10%+ reply rate with a 40%+ positive reply rate, but the discovery call conversion rate from interested replies to booked meetings is below 20%.
Cause 1: Reply management speed is too slow. Interested replies that are not followed up within 4 hours have significantly lower meeting conversion rates. Cause 2: The follow-up to an Interested reply is another automated email rather than a personalised response with a specific calendar link. Cause 3: The meeting booking process requires too many steps (multiple email exchanges before a time is agreed).
Fix: Implement a calendar link in the first reply to any Interested label. Respond to all Interested replies within 2–4 hours. Use Calendly or an equivalent tool to make meeting booking a single-click action from the reply.
Symptom: A campaign that was expected to run for 30 days is exhausting the contact list in 10–12 days.
Cause: The daily send limit is higher than planned, or the contact list was smaller than expected after deduplication and bounce removal.
Fix: Source additional contacts from Quarvio before the list is exhausted. Use the Quarvio capacity planning table in Layer 1 to pre-calculate the contacts needed for the target campaign duration and daily volume. Source 20% more contacts than the theoretical requirement to account for deduplication and bounce removal.
Symptom: Aimfox is sending connection requests but fewer than 1 in 5 are being accepted.
Cause 1: The connection request message is too long or too salesy. LinkedIn connection requests with a message that reads like a sales pitch have lower acceptance rates than requests with a brief, non-commercial message. Cause 2: The LinkedIn profile of the sending account does not present as credible for the ICP being targeted. Cause 3: The ICP targeting in Aimfox does not match the job titles and company types of the contacts being reached.
Fix: Shorten the connection request message to under 100 characters. Make it personal and non-commercial: referencing a shared connection, a specific post, or a recent company event. Review the LinkedIn profile of the sending account to ensure it presents a credible professional background relevant to the outreach.
Symptom: Bounce rate was under 2% in the first two weeks but spikes to 5–8% in week 3.
Cause: The contact list for the third week of sends contains contacts with higher bounce risk — typically contacts sourced from older data, contacts at smaller companies with less stable email infrastructure, or contacts who have recently changed roles.
Fix: Re-verify the contact list before the third week of sends. For Quarvio contacts, this verification is already done; the spike is more likely from a mixed-source list containing non-Quarvio contacts with older data. Pause the campaign, remove contacts with bounce risk indicators (job title changes, company size under 10 employees at domain providers with poor infrastructure), and resume at 50% daily volume.
Symptom: Instantly shows "inbox error" or "authentication failed" for one or more Inframail inboxes.
Cause: SMTP credentials have changed, password has expired, or Microsoft 365 has flagged the account for unusual activity (automated send patterns without prior warmup history).
Fix: Re-authenticate the affected inboxes in Instantly with updated credentials from Inframail. Reduce daily send volume on the reconnected inbox by 50% for 3 days to avoid triggering Microsoft 365's automated anomaly detection.
Symptom: LinkedIn restricts the account used for Aimfox, requiring phone verification or reducing connection request limits.
Cause: The connection request volume exceeded LinkedIn's detection threshold, or the account is new and has not established natural LinkedIn usage history before automation began.
Fix: Per LinkedIn's automation policy, reduce connection request volume to 15–20 per day. Ensure the LinkedIn account has at least 500 existing connections and at least 4 weeks of natural usage before starting automation. Use Aimfox's built-in safety limits to stay within LinkedIn's detection thresholds.
Woodpecker's 2025 cold email benchmark study reports that multichannel outreach (email + LinkedIn) consistently outperforms single-channel email by 40–60% in total reply rate. The benchmark study identifies contact list quality as the highest-leverage variable in outbound performance, ahead of email copy, subject line quality, and sending frequency. Teams using verified contact data from a dedicated source achieve average reply rates of 8.5% versus 3–4% for teams using unverified or self-sourced lists.
Instantly's 2026 cold email benchmark report shows that the average Instantly user achieves a 3.43% reply rate, while the top 10% of users achieve above 10%. The primary differentiating factor between average and top-10% performers is ICP precision: teams with narrowly defined ICPs using verified contact data consistently reach the top decile, while teams with broad ICPs using unverified contact data cluster near the bottom.
"The single biggest change we made was buying the stack in the right order. We used to have Instantly before we had proper inboxes, so we were burning our main domain. When we switched to Inframail for dedicated inboxes and Quarvio for the contact lists, the delivery rate went from about 60% to above 95%. The stack itself is simple; the build order is what took us 6 months to figure out." — G2 reviewer, Instantly reviews on G2
| Need | Tool | Notes |
|---|---|---|
| Verified B2B contacts | Quarvio | One-time purchase, no subscription |
| Email inboxes | Inframail | Microsoft 365 inboxes, auto DNS |
| Cold email sending | Instantly | Sequences, warm-up, reply tracking |
| LinkedIn outreach | Aimfox | Connection campaigns, parallel outreach |
What are the four layers of a B2B outreach stack?
The four layers are: contact data (Layer 1 — who you reach), email infrastructure (Layer 2 — what sends the email), email sequencing (Layer 3 — how you sequence the outreach), and LinkedIn automation (Layer 4 — multichannel reinforcement). Each layer depends on the layer below it: you cannot run sequences (Layer 3) without inboxes (Layer 2), and inboxes (Layer 2) are useless without contact data (Layer 1). The correct build order is 1 → 2 → 3 → 4.
What is the total monthly cost of a standard B2B outreach stack?
A standard 10-inbox operation sending 500 emails per day across 5–6 domains typically costs $350–$500/month in recurring tool costs (Inframail flat-rate inboxes + Instantly Growth or Hypergrowth plan + Aimfox Solo plan). Contact data from Quarvio is a one-time purchase: the Scale package (25,000 contacts / $399) provides approximately 30 days of sends at 500/day, with credits valid for 12 months. Total first-month cost including contact data: $750–$900. Subsequent months: $350–$500 (recurring tools only, using remaining Quarvio credits).
Why use separate sending domains instead of the primary company domain?
Sending cold email from the primary company domain (company.com) risks permanently damaging the domain's email reputation. All company email (transactional receipts, internal email, customer support) shares the same domain reputation as the cold outreach. If cold email generates spam complaints, the primary domain reputation suffers, which can cause transactional emails to land in spam — a far more damaging consequence than the cold email performance issue. Cold email domains isolate outreach reputation from the primary domain completely.
How long does warmup take before a new inbox can be used for production sends?
Per Woodpecker's email warmup guide, 2–4 weeks of warmup is the minimum before production sends, and 8–12 weeks produces full reputation maturity. The practical milestone is when Google Postmaster Tools shows "High" domain reputation — do not start production sends before this milestone is reached regardless of the number of warmup days completed. Instantly's warmup system handles this automatically for connected inboxes.
What is inbox rotation and why does it matter?
Inbox rotation is the automatic distribution of sends across multiple inboxes within a campaign, ensuring no single inbox exceeds its daily send limit. If a campaign is assigned 5 inboxes with a 40-send daily limit each, inbox rotation allows the campaign to send up to 200 emails per day while keeping each inbox within the 40-send limit. Without inbox rotation, a campaign using a single inbox would hit the daily limit after 40 sends and stop for the day. Instantly handles inbox rotation automatically when multiple inboxes are assigned to a campaign.
Can the four layers be replaced by different tools?
Yes, the layer architecture is tool-agnostic: any verified contact data source can fill Layer 1, any inbox provider can fill Layer 2, any cold email sequencing tool can fill Layer 3, and any LinkedIn automation tool can fill Layer 4. However, the integration overhead increases when substituting tools: Quarvio, Inframail, Instantly, and Aimfox are designed to work together, and the data flow between them requires minimal manual coordination. Substituting any layer requires re-establishing the data flow between the new tool and the adjacent layers.
How many inboxes do I need to send 1,000 cold emails per day?
At the recommended limit of 40–50 emails per warmed inbox per day, 1,000 emails per day requires 20–25 inboxes. Distribute across 10–12 sending domains (2–3 inboxes per domain) to isolate reputation by domain. Inframail provisions inboxes at flat-rate pricing regardless of volume, making high-inbox-count operations economical.
What is the build order for a B2B outreach stack?
Build in this exact order: (1) purchase contact data from Quarvio, (2) provision sending domains and inboxes via Inframail, (3) authenticate domains with SPF, DKIM, DMARC, (4) connect inboxes to Instantly and start warmup, (5) wait for warmup to reach "High" reputation, (6) import Quarvio contacts and build sequences in Instantly, (7) start Aimfox LinkedIn campaign targeting the same ICP, (8) monitor Unibox and respond to positive replies within 4 hours. Any deviation from this order creates rework.
How does LinkedIn (Layer 4) integrate with email (Layer 3)?
Layer 4 runs in parallel with Layer 3, targeting the same ICP contacts on LinkedIn. The timing synchronisation rule is: start the Aimfox LinkedIn campaign on Day 2–3 of the Instantly email sequence. The email arrives first, introducing the message; the LinkedIn connection request arrives 1–2 days later, reinforcing it. This timing produces higher combined response rates than either channel alone or than LinkedIn arriving before email.
What metrics should I track for each layer of the stack?
Layer 1 (contact data): list quality score (% of contacts matching ICP criteria), email validity rate, bounce rate on first send. Layer 2 (infrastructure): domain reputation in Postmaster Tools, spam rate per domain, inbox health score. Layer 3 (sequences): open rate, reply rate, positive reply rate, bounce rate. Layer 4 (LinkedIn): connection acceptance rate, message reply rate, total LinkedIn conversations started. The most important cross-layer metric is total pipeline generated (discovery calls booked) as a function of total contacts reached across both channels.
How do I know if my contact list quality is the problem vs. my email copy?
Run a copy test: take your best-performing email copy from a previous campaign and run it against a fresh Quarvio contact list for the same ICP. If reply rate improves significantly with the same copy and different list, the original list was the problem. If reply rate stays low with the same copy and a fresh list, the copy is the problem. This test takes 200–300 sends to produce reliable data. The most common finding is that the contact list quality is the primary driver of underperformance, not the copy — which is why Layer 1 is the foundation of the entire stack.
What is the right number of emails in a cold outreach sequence?
Per Instantly's 2026 benchmark report, 3–5 email sequences consistently outperform single emails and sequences of 6+ emails on total reply generation. A 4-email sequence over 12–14 days (Email 1 on Day 1, Email 2 on Day 3–4, Email 3 on Day 7–8, Email 4 on Day 12–14) captures the majority of total replies while staying within the timing window where the original message is still relatively fresh in the prospect's memory.
Build your outreach stack on verified contacts.
The quality of your Layer 1 contact data determines the ceiling of everything else in the stack. Quarvio delivers verified B2B contacts matched to your ICP — one-time purchase, credits valid for 12 months, no subscription. Start with the contacts; build the rest of the stack around them.
