Run messaging for one client and almost any inbox works. Run it for ten and the cracks show within a week: a WhatsApp lead for Client A gets answered in Client B's voice, nobody knows which teammate owns which conversation, SMS lives in a totally different tab, and your "all-in-one" tool turns out to charge per seat per brand. A real multichannel shared inbox fixes all of that — it pulls WhatsApp, Instagram, Messenger, SMS and web chat into one screen and keeps each client cleanly separated, without bleeding your retainer margin into license fees.
This is an agency-first ranking. The deciding factors aren't "is the UI pretty." They're how the tool handles a roster of clients, whether outbound WhatsApp actually works at scale, whether you can white-label it, and what your contribution margin looks like once you've added every channel, every seat and every client. We've weighted the list accordingly.
How we evaluated these tools
We score shared inboxes the way an agency operator actually feels them — on the P&L and on the worst Monday of the month, not on the demo. Five criteria, weighted:
- Client separation (25%). Sub-accounts, workspaces or teams that keep Client A and Client B fully isolated — branding, data, billing and routing — under one operator login. This is the make-or-break for agencies and the thing consumer inboxes get wrong.
- Channel breadth and outbound reality (25%). WhatsApp and Instagram are table stakes. The real test is outbound WhatsApp outside the 24-hour window, which needs approved templates and a provisioned (or bring-your-own) sender on the WhatsApp Business Platform.
- Routing, assignment and AI assist (20%). SLA timers, internal notes, round-robin, and an AI layer that drafts or fully handles replies. The boring stuff that stops dropped leads.
- Margin and pricing curve (20%). Per-seat plus per-contact pricing compounds fast across a roster. We model the curve at 5–10 clients, not at one.
- White-label and resale (10%). Custom domain, logo, and the ability to resell to clients as your own product — the difference between a cost centre and a profit line.
We pulled pricing pages, BSP documentation and hands-on setup notes for each tool. Where exact prices move around (they all do), we describe the shape of the cost rather than fabricate a number.
What separates an agency inbox from a startup inbox
Most "team inbox" tools are built for a single growing company, not for an operator running messaging on behalf of others. The gap shows up in five places:
- Client separation. Sub-accounts, workspaces or teams so two clients never bleed into each other. A single shared workspace with "tags" is not separation — it's a data-leak incident waiting to happen.
- True multichannel. WhatsApp and Instagram are non-negotiable now; Messenger, SMS and web chat should be first-class, not bolt-ons. If you're heavy on Instagram specifically, our roundup of the best AI chatbots for Instagram DMs goes deeper on that channel.
- Outbound WhatsApp reality. Sending outside the 24-hour window means approved templates and a provisioned or BYO sender. This is where tools quietly differ — some hold your hand through Meta verification, others hand you a Twilio key and wish you luck.
- Routing and assignment. Who owns the conversation, SLA timers, internal notes, escalation. Unsexy, but it's what stops leads dying in an unassigned queue.
- Cost as you scale. Per-seat plus per-contact pricing across a roster adds up brutally. Know the curve before you sign clients onto it, and read our guide to pricing AI services as an agency before you set retainers.
The ranking at a glance
| Tool | Best for | Client separation | Channels | White-label | Pricing feel |
|---|---|---|---|---|---|
| Respond.io | Multi-client teams | Workspaces | WA, IG, FB, SMS, web | Partial | Mid-to-upper |
| WATI | WhatsApp-first agencies | Per number | WhatsApp-centric | Limited | Mid-range |
| DM Champ | DM closing + white-label resale | Sub-accounts | WA, IG, FB, TG, SMS, web, email | Full | From low monthly + LTD |
| Trengo | SMB service inboxes | Teams | WA, IG, FB, email, voice | Limited | Mid-range |
| Front | Email-led operations | Shared mailboxes | Email-first + social | No | Upper |
| Intercom | Support at scale | Workspaces | Web + social + email | No | Premium |
Capability matrix
| Platform | Sub-accounts | WhatsApp API | IG + Messenger | AI agent | White-label | Resell to clients |
|---|---|---|---|---|---|---|
| ★Respond.io | ✓ | ✓ | ✓ | ✓ | ~Partner | ~ |
| WATI | ~ | ✓ | ~Add-on | ~ | ✕ | ✕ |
| DM Champ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Trengo | ~ | ✓ | ✓ | ~ | ✕ | ✕ |
| Front | ~ | ~Via BSP | ~ | ~ | ✕ | ✕ |
| Intercom | ✓ | ~Via BSP | ✓ | ✓ | ✕ | ✕ |
1. Respond.io — best all-round agency inbox
Respond.io is the strongest general-purpose pick for agencies running several clients across channels. Workspaces keep clients separate, channel coverage is broad and reliable, routing and AI-assist are mature, and it handles the WhatsApp Business API properly — including the verification and template lifecycle that trips up lighter tools. For an operator who wants one dependable inbox that won't embarrass them in front of an enterprise client, this is the safe, serious choice.
Pros: genuine multi-channel breadth, solid team and routing features, capable automation builder, and a partner program if you want to position around it.
Cons: pricing climbs as you add contacts and seats, so model the curve before you onboard a roster; and it's more inbox than CRM, so deep pipeline reporting still lives elsewhere. It's also a configuration-heavy tool — powerful, but not something a junior account manager spins up in an afternoon. Our full Respond.io review digs into the workspace model and where the per-contact billing bites.
2. WATI — best if you're WhatsApp-first
If 80% of your clients' volume is WhatsApp, WATI is purpose-built for it: team inbox, broadcast, template management and chatbot flows on the WhatsApp Business API, with a setup flow that's genuinely friendly for non-technical operators. For agencies serving markets where WhatsApp is the channel — much of LATAM, MENA, India, Southern Europe — it's hard to beat on focus.
Pros: deep WhatsApp tooling, approachable pricing, clean broadcast and template management.
Cons: other channels are thin, so a truly multichannel roster will outgrow it, and the agency multi-tenant story is weaker than the workspace-native tools. If you want the WhatsApp depth without committing your whole roster, our WATI review covers where it shines and where it stalls.
3. DM Champ — best when the inbox is for closing, not just support
DM Champ puts WhatsApp, Instagram, Messenger, Telegram, SMS, web chat and email into one shared inbox, but its angle is different from everything else on this list: it's built around an AI sales agent that qualifies, handles objections and books appointments inside the conversation, rather than around a human help-desk queue. For agencies the resale story is the real draw — sub-accounts per client, custom domain and logo, and the ability to resell credits to clients through Stripe, plus BYOK if you'd rather manage AI spend on your own provider keys. Pricing starts from $27/mo with a lifetime deal on AppSumo, which makes the unit economics unusually friendly when you're stacking clients.
It also closes the loop on top-of-funnel: built-in comment-to-DM means Instagram and Facebook comments can trigger a DM thread that lands straight in the same inbox, so the lead source and the closing surface are one system. If that funnel is central to you, pair this with our best comment-to-DM automation tools roundup.
Honest cons: it's a younger, smaller brand than Respond.io or Intercom, so third-party reviews and community are thinner — if procurement at a large client wants a Gartner reference, this isn't it yet. It's built around DM-based closing rather than being a full help desk or CRM, so ticketing depth and contact-record reporting are lighter. And the deeper features — custom AI functions, BYOK routing, sub-account credit resale — have a real learning curve; you'll spend a session or two before it sings. If you want a pure support inbox with deep ticketing, look elsewhere; if you want one white-label inbox that also drives sales across a client roster, it's a strong fit. DM Champ.
4. Trengo — best for SMB service inboxes
Trengo is a clean, friendly multichannel inbox aimed at SMB customer service, with WhatsApp, social, email and voice in one view and tidy team features on top. For agencies whose clients are local service businesses fielding day-to-day customer questions, it onboards quickly and looks good doing it.
Pros: easy to onboard clients, good channel mix including voice, pleasant UI.
Cons: less of an agency multi-tenant story — you'll lean on teams rather than true sub-accounts — and the AI layer is lighter than the leaders. It's a service inbox first, a sales engine second.
5. Front — best for email-led operations
Front is the pick when your agency's communication is email-heavy and social is the side dish. Shared mailboxes, assignment, internal comments and collaboration are genuinely best-in-class, and it integrates with almost everything.
Pros: superb email collaboration, strong integration catalogue, mature assignment and analytics.
Cons: social and chat channels are secondary and often routed through third-party connectors, and pricing sits at the upper end for what is, at heart, an email tool. If WhatsApp and Instagram are your primary surfaces, this is the wrong centre of gravity.
6. Intercom — best for support at scale
Intercom (with its Fin AI agent) is the heavyweight for product-led support across web, social and email. If a client needs serious help-desk depth — workflows, macros, knowledge base, deflection metrics — it's excellent and it scales. For comparison against the other obvious enterprise pick, see Intercom vs Zendesk for agencies.
Pros: powerful AI agent, deep support tooling, strong reporting.
Cons: premium pricing that's hard to justify for lead-gen, and a support-desk mindset that's overkill for DM closing. WhatsApp typically runs through a BSP connector rather than native provisioning. You buy Intercom to deflect tickets, not to book sales calls.
Pricing: model the curve, not the sticker
The headline price on every one of these tools is a trap. What matters to an agency is the curve — what you pay once you've added six clients, a dozen seats and tens of thousands of contacts. Per-contact billing in particular has a way of turning a "$79/mo" inbox into a four-figure invoice by client number eight.
Two structural costs hide behind every sticker. First, WhatsApp conversation and template fees are charged by Meta on top of your software bill on every platform here — budget for them separately. Second, seats: a tool that charges per seat per client workspace will quietly outpace a tool with operator-level sub-accounts as you grow. That second factor is exactly why white-label resale tools change the maths — you're marking the license up to the client, not just absorbing it. If resale is your model, our white-label chatbot platforms for resellers comparison is the companion read.
Positioning: where each tool actually sits
Price alone is half the picture. The other half is capability — how much of your messaging operation a tool can actually run. Plot the two together and the agency-relevant clusters become obvious: power buys in the top-left, premium tools in the top-right, and a couple of options that are either narrow or pricey for what they do.
Weighted scorecard
Against our five-criteria framework, here's how the two most agency-shaped options stack up head to head — the broad generalist versus the resale-and-closing specialist.
How to choose
For most agencies running several clients across channels who want a dependable, well-known generalist, start with Respond.io. WhatsApp-dominant rosters do well on WATI. If the inbox's real job is to convert leads — and you want to white-label and resell it as your own product line — DM Champ is the pick that protects margin. Email-led shops want Front, SMB service teams suit Trengo, and clients needing serious support-desk depth justify Intercom.
A few decision shortcuts:
- Optimising for resale margin? You want full white-label and operator-level sub-accounts, which narrows the field fast. Pair the inbox choice with our playbook on building a recurring-revenue agency with AI.
- Optimising for breadth and enterprise credibility? Respond.io or Intercom, and accept the pricing curve.
- Optimising for a single dominant channel? WATI for WhatsApp, or revisit the dedicated Instagram tools if IG is your battleground.
- Reporting matters as much as replying? No inbox here is a true reporting suite — plan to connect one. Our AI tools for agency client reporting roundup covers the layer that sits on top.
One rule regardless of tool: pick based on how it handles your worst-case client load, not your first client. The inbox that feels great with one brand and falls apart at eight is the most expensive mistake in this category — you'll have migrated half a roster before you admit it, and migrations during a live retainer are brutal. Model the curve at ten clients, demand real client separation, and confirm outbound WhatsApp works the way your clients need before a single lead lands in the queue.