Compare/Head to head

Master Inbox vs OutboundSync

Same facts, side by side: starting price, free tier, MCP, API and what each one is actually built for.

Starting price

Master Inbox

$599/mo

Master Inbox collects every cold email and LinkedIn reply from your sequencers into one AI-labeled inbox, with a separate workspace for each client. It suits outbound agencies and recruiting firms running business development across many mailboxes and clients. Plans start at $599 a month on annual terms billed monthly, and the vendor runs a free 7-day proof of concept on your own inboxes.

Where Master Inbox fits

  • Outbound agencies managing replies for many clients
  • Teams running several sequencers and LinkedIn tools at once
  • Agencies that want to give clients a scoped inbox login
  • RevOps leads tracking missed replies and response time

Syncs Smartlead, Instantly, and other outbound tools into Salesforce and HubSpot. Starter is $99/mo for 2,000 sends.

Where OutboundSync fits

  • Teams pushing Instantly or Smartlead into Salesforce
  • HubSpot shops that want outbound events in the CRM
  • Ops teams that refuse Zapier for send logging
  • Companies that need SOC 2 on the sync layer

At a glance

DetailMaster InboxOutboundSync
Starting price$599/mo$99/mo
Free tier–No–No
MCP server–No–No
Public API✓Yes✓Yes
Listed underOutreach, Workflow automationLead generation, Outreach, CRM

Where they pull apart

Master Inbox

Stands out: It reads the mailboxes themselves rather than relying on the sequencer's reply feed, so forwards, CC replies and replies from new addresses show up alongside the rest, which a sequencer unibox such as Instantly's can miss. Unlimited users on every plan and per-client workspaces with scoped client logins make it built for agencies that hand reply handling to a team.

Watch out: The entry price of $599 a month is high for a solo recruiter or a small desk, and month to month billing adds 25%. Native Salesforce sync is not available yet and runs through webhooks or the OutboundSync partnership, and AI usage is paid separately on your own model key.

Not the right fit for

  • Solo recruiters with a handful of mailboxes
  • Teams that need native Salesforce sync
  • Buyers who want a low monthly entry price

OutboundSync

Stands out: API, webhooks, and agent skills ship on every plan, with unlimited connectors and SOC 2 Type II.

Watch out: You are billed on sent messages, not replies or opens. Staying over plan plus 2x rollover can pause sync. Annual pre-pay is two months free.

Not the right fit for

  • In-house teams that already log sends natively
  • Very high volume unless you buy Custom

Pros and cons

Master Inbox

  • Unlimited users on every plan
  • Catches forwards and replies sequencers miss
  • Per-client workspaces with scoped logins
  • Starts at $599 a month
  • Salesforce not native yet
  • AI usage billed on your own model key

OutboundSync

  • Starter $99/mo for 2,000 sends
  • API and webhooks on every plan
  • SOC 2 Type II on the sync layer
  • Overages can pause CRM sync
  • Billed on sends, not outcomes
  • Walkthrough required to buy

What each one costs

Master Inbox

$599/mo

Master Inbox prices on client workspaces and mailboxes, with unlimited users on every plan. Listed prices are annual, billed monthly; month to month costs 25% more and annual prepaid saves 15%. For agencies, Agency is $599 a month for 15 client workspaces and 3,000 mailboxes, Scale is $1,297 a month for 40 workspaces and 15,000 mailboxes, and Unlimited is $1,697 a month for unlimited workspaces and 30,000 mailboxes. A Ramp option for agencies with fewer than five clients starts at $299 a month with a $500 onboarding fee that is credited back. For in-house teams, Team is $799 a month for 2,000 mailboxes and Revenue is $1,499 a month for 7,500 mailboxes. Enterprise and the white-label Platform plan start at $2,500 a month on annual terms. The vendor offers a free 7-day proof of concept on your own inboxes. Confirm current terms on the vendor site.

Checked 4 Nov 2026

OutboundSync

$99/mo

Starter is $99/mo for 2,000 sent messages (2x rollover to 4,000). Explorer is $249/mo for 10,000. Advanced is $499/mo for 25,000. Custom is annual. Monthly billing. Annual pre-pay gives two months free. API access and unlimited connectors on every plan. Confirm current terms on the vendor site.

Checked 4 Nov 2026

Common questions

Is Master Inbox cheaper than OutboundSync?
OutboundSync starts lower, at $99/mo against $599/mo for Master Inbox. That is the entry plan on each side, so the real number depends on seats and the tier you land on.
Can you try Master Inbox or OutboundSync for free?
Neither carries a free tier on our listing.

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Editorial listings, never paid rankings. Prices checked 4 Nov 2026. Confirm current terms on the vendor site. Spot an error?