Multi-Client Outbound for Agencies

Help the user architect, scale, and operate outbound infrastructure for a lead generation agency — from client isolation and domain strategy through warmup at scale, onboarding playbooks, and cross-client reporting. This skill is tool-agnostic and covers Smartlead, Instantly, Mailshake, and multi-tool setups.

Step 1 — Gather context

Ask the user:

1. How many clients do you serve (or plan to)?

   • A) Starting out — 1-3 clients
   • B) Growing — 4-10 clients
   • C) Scaled — 10-25 clients
   • D) Enterprise agency — 25+ clients

2. What's the typical sending volume per client?

   • A) Light — under 100 emails/day
   • B) Standard — 100-500 emails/day
   • C) High volume — 500-2,000 emails/day
   • D) Varies widely across clients

3. What tooling are you using?

   • A) Smartlead (unlimited mailboxes, master inbox)
   • B) Instantly (bulk warmup, simple UI)
   • C) Mailshake (Lead Catcher, CRM integration)
   • D) Apollo (prospecting + sequences)
   • E) Mix of tools — describe
   • F) Haven't decided yet

4. What's your client onboarding process today?

   • A) Ad hoc — no standard process
   • B) Have a rough checklist but it's inconsistent
   • C) Documented and repeatable
   • D) Starting from scratch — need to build it

5. What's your biggest challenge right now?

   • A) Setting up infrastructure for the first time
   • B) One client's issues affecting others (cross-contamination)
   • C) Scaling — adding clients without proportional ops work
   • D) Reporting — clients want better visibility
   • E) Deliverability across multiple domains/clients
   • F) Something else — describe it

6. Do you need white-labeling? (client-facing branding)

7. What's your team structure? (solo founder, small team, dedicated account managers per client)

If the user's request already provides most of this context, skip directly to the relevant step. Lead with your best-effort answer using reasonable assumptions (stated explicitly), then ask only the most critical 1-2 clarifying questions at the end — don't gate your response behind gathering complete context.

Step 2 — Architecture decisions

Infrastructure model

Choose the right isolation level based on client count, volume, and risk tolerance:

Model	How it works	Best for	Risk level
Shared mailboxes	Agency-owned mailboxes used across clients	Solo operator, 1-2 clients, testing	High — one client's reputation affects all
Dedicated per client	Each client has their own domains + mailboxes	3+ clients, any volume	Low — full isolation
Hybrid	Dedicated domains per client, shared infrastructure (IPs)	Budget-conscious, low-volume clients	Medium — domain-level isolation without IP isolation

Recommendation: Always use dedicated per client for domain and mailbox isolation. The cost of a single cross-contamination incident (blacklisted domain, cascading reputation damage) far exceeds the cost of separate domains.

Domain strategy

Decision	Recommendation	Rationale
Domain ownership	Client-owned preferred, agency-provisioned acceptable	Client keeps the asset; if they leave, their domain goes with them
Domains per client	1 domain per 3-5 mailboxes	Distributes reputation risk; losing one domain doesn't kill the campaign
Domain naming	{client}mail.com, get{client}.com, try{client}.com	Close to brand but clearly separate from primary domain
Primary domain protection	Never send cold outbound from the client's primary domain	If outbound domain gets blacklisted, primary email is protected

Example: Client "Acme Corp" (acme.com) gets:

• acmemail.com — 5 mailboxes (jane@, mike@, sarah@, tom@, alex@)
• getacme.com — 5 mailboxes (as backup/rotation domain)
• acme.com — never used for cold outbound

Warmup at scale

Managing warmup across 20+ mailboxes requires planning:

Phase	What to do	Timeline
Stagger starts	Don't start all mailboxes on the same day — stagger by 2-3 days per batch of 5	Days 1-10
Monitor reputation	Check warmup reputation scores daily — all mailboxes should reach 80+ before campaign sends	Weeks 1-3
Gradual activation	Add warmed mailboxes to campaigns in batches, not all at once	Week 3+
Ongoing warmup	Keep warmup running even during active campaigns — it supplements reputation	Continuous

Tool selection matrix

Feature	Smartlead	Instantly	Mailshake
Unlimited mailboxes	Yes (all plans)	Yes (Growth plan)	No (plan-based limits)
Built-in warmup	Ultra Premium Warmup	Warmup pool	No (use external)
Master inbox	Yes — unified across clients	Limited	No
Client workspaces	Yes — native isolation	Yes — workspace management	Limited — team member isolation
White-label	Yes (higher plans)	No	No
API for automation	Yes	Yes	Yes
Best for agency use	Full-featured agency platform	Simple multi-client warmup	Single-client with CRM focus

Step 3 — Client onboarding playbook

Repeatable checklist for onboarding each new client:

Phase 1: Infrastructure (Days 1-3)

1. Domain provisioning

   • Register 2 outbound domains (primary + backup) per client
   • Point DNS to your email provider
   • Configure SPF, DKIM, DMARC for each domain (→ /sales-deliverability)

2. Mailbox creation

   • Create 3-5 mailboxes per domain (real names, professional formatting)
   • Connect via OAuth (Gmail/Outlook) or SMTP
   • Set daily limits: 30-50 per mailbox

3. Warmup scheduling

   • Enable warmup on all mailboxes immediately
   • Stagger start dates if provisioning 10+ mailboxes
   • Target: 2-3 weeks warmup before first campaign send
   • Monitor warmup reputation daily

Phase 2: Campaign setup (Days 3-7)

4. ICP definition + list building (→ /sales-prospect-list)

   • Define target persona with client input
   • Build initial prospect list (200-500 for first campaign)
   • Verify emails before import

5. Cadence design (→ /sales-cadence)

   • Design email sequence (3-5 steps, 7-14 day cadence)
   • Write email copy with client-approved messaging
   • Set up A/B tests for subject lines

6. Integration setup (→ /sales-integration)

   • Connect to client's CRM (if applicable)
   • Set up lead forwarding (webhook, Zapier, or email)
   • Configure Slack/email notifications for interested replies

Phase 3: Launch (Days 14-21)

7. Go-live checklist
   • All mailboxes have 80+ warmup reputation
   • DNS records verified (SPF/DKIM/DMARC passing)
   • SmartDelivery or mail-tester.com shows inbox placement
   • Prospect list verified (<3% expected bounce rate)
   • Email copy approved by client
   • CRM/notification integration tested
   • Daily sending limits configured correctly
   • Campaign activated with small initial batch (50-100 leads)

Step 4 — Reporting and operations

Client-facing metrics

Report what clients actually care about — not vanity metrics:

Metric	What to report	Cadence
Meetings booked	Total meetings booked, cost per meeting	Weekly
Pipeline generated	Dollar value of opportunities created	Monthly
Interested replies	Leads who expressed interest (qualified replies)	Weekly
Reply rate	Positive reply rate (not total replies)	Weekly
Campaign health	Active campaigns, leads in pipeline, next steps	Weekly

Avoid reporting: Raw open rates (unreliable with Apple MPP), total sends, click rates (meaningless for cold outbound). Clients who fixate on opens/clicks will micromanage the wrong things.

Internal ops metrics

Track these internally to spot issues before clients notice:

Metric	Target	Action if exceeded
Bounce rate (per client)	<3%	Pause campaign, verify remaining list, investigate domain
Warmup reputation (per mailbox)	80+	Remove from campaign rotation, investigate
Cross-client deliverability	<5% variance in inbox placement	Investigate outlier clients for contamination
Mailbox utilization	60-80% of daily limit	Scale up if >80%, investigate if <40%
Warmup pipeline	2+ weeks ahead of new campaigns	Provision mailboxes earlier

Scaling patterns

Trigger	Action
Client reaches daily limit	Add mailboxes (1 per 50 emails/day needed)
Client adds new persona	New domain + mailboxes for isolation
Bounce rate creeping up	Rotate to fresh domain, investigate list quality
New client onboarded	Follow Phase 1-3 playbook (14-21 day ramp)
Client churns	Decommission domains (don't reuse for other clients)

Step 5 — Platform-specific implementation

In Smartlead

• Master inbox: Unified view across all client campaigns — manage replies from one interface
• Client workspaces: Create a workspace per client (Settings > Clients). All campaigns, leads, and sender accounts scoped to the workspace.
• White-label: Settings > White Label — custom domain, logo, colors for client-facing access
• Unified analytics: Cross-client performance dashboard with per-client drill-down
• SmartSenders: Bulk-provision mailboxes per workspace. Warmup runs per-mailbox automatically.

In Instantly

• Workspace management: Create separate workspaces per client for isolation
• Bulk warmup: Instantly's warmup pool handles large mailbox counts efficiently
• Campaign organization: Name campaigns with client prefix (e.g., "Acme - Q1 VP Eng")
• Limitation: No native white-label or master inbox — less agency-friendly than Smartlead

In Mailshake

• Team member isolation: Assign team members per client, but isolation is weaker than workspace-based tools
• Lead Catcher: Useful for per-client reply management, but no master inbox across clients
• CRM integration: Strong native CRM integration (Salesforce, HubSpot) — good if clients require direct CRM sync
• Limitation: Plan-based mailbox limits make scaling expensive for agencies

In Reply.io

• Agency plan: Dedicated Agency plan (~$166/mo) with unlimited clients and unlimited users
• Client isolation: Each client gets isolated sequences and contact lists
• Unified dashboard: Manage all clients from a single dashboard
• Built-in warmup: Warmup for all client mailboxes included
• API access: Programmatic client management — create seats, add mailboxes via Master API Key

In Woodpecker

• Agency panel: Add-on at €27/month per active client — manage all clients from a single dashboard
• Client isolation: Each client gets separate campaigns, prospects, mailboxes, and deliverability settings
• Agency API: HQ API key + x-company-id header to manage clients programmatically — create API keys per company, manage mailboxes and campaigns across clients
• Per-client warmup: Each client's mailboxes get independent warmup slots — no cross-contamination of sender reputation
• Pricing model: Scales per active client (€27/client) + per contacted prospects tier. Compare: Smartlead has flat agency pricing, Woodpecker scales linearly.
• White-labeling: Not natively supported — agency panel is Woodpecker-branded

Cross-platform setup

• Some agencies use different tools for different clients based on client needs (e.g., Smartlead for high-volume, Mailshake for CRM-heavy clients)
• Standardize reporting across tools — use a shared dashboard (Google Sheets, Looker, or custom) that aggregates metrics from all platforms
• Maintain per-client tool documentation so any team member can pick up any client

Gotchas

• Don't share sending domains across clients. One client's reputation meltdown (high bounces, spam complaints, blacklisting) poisons all clients sharing that domain. The cost of a $12/year domain is nothing compared to rebuilding reputation for 5 clients.
• Don't skip per-client warmup. New domains need their own warmup regardless of mailbox age. Even if you're reusing an established mailbox on a new domain, the domain itself has zero reputation. Follow the full warmup schedule.
• Don't report vanity metrics. Report meetings booked and pipeline generated, not opens and clicks. Clients who focus on opens will micromanage subject lines instead of trusting the process. Set expectations during onboarding about which metrics matter.
• Don't use a single Zapier account for all clients. Billing, rate limits, and error handling cascade across all zaps in one account. If one client's integration breaks and triggers retries, it can exhaust your Zapier task quota and break every other client's integration. Use separate Zapier accounts or a dedicated integration layer.

Related skills

• /sales-smartlead — Smartlead platform help (SmartSenders, SmartInfra, campaigns, API)
• /sales-deliverability — Domain authentication, warmup schedules, inbox placement
• /sales-cadence — Design outbound cadences and email content
• /sales-prospect-list — Build targeted prospect lists for client campaigns
• /sales-integration — Connect outbound tools to CRM via webhooks, Zapier, or API
• /sales-mailshake — Mailshake platform help
• /sales-reply — Reply.io platform help (Agency plan with unlimited clients)
• /sales-woodpecker — Woodpecker platform help (Agency panel with per-client management)
• /sales-do — Not sure which skill to use? The router matches any sales objective to the right skill.

Examples

• "First 3 clients on Smartlead" → Dedicated domains per client (2 each), 3-5 mailboxes per domain via SmartSenders, client workspaces for isolation, staggered warmup plan, Phase 1-3 onboarding checklist
• "Client blacklisted, other clients' rates dropping" → Diagnose shared domain/IP as cross-contamination cause, pause affected client, check blacklists, provision new domains, re-warmup, design strict per-client isolation going forward
• "Build repeatable onboarding process" → Phase 1-3 playbook (14-21 days), reusable checklist template, handoffs to /sales-prospect-list, /sales-cadence, /sales-integration, client kickoff questionnaire, milestone tracking