OutboundSync + Master Inbox: HubSpot and Salesforce Sync
On this page
- What is OutboundSync?
- Why does an outbound team need OutboundSync when it already has Master Inbox?
- How do Master Inbox and OutboundSync work together?
- How do you set it up?
- When is Master Inbox's HubSpot Suite enough, and when do you add OutboundSync?
- What do customers who run both say?
- Thank you, OutboundSync
- FAQs
OutboundSync published a partner spotlight on Master Inbox on 24 September, written by Jason Ma. It is generous, it is accurate, and it prompted this post, because the question we get on almost every HubSpot or Salesforce call is the same: what does Master Inbox sync into the CRM, what does OutboundSync sync, and do I need both? Short version: if you report on outbound inside HubSpot or Salesforce, run both. Here is why, and how they fit.
What is OutboundSync?
OutboundSync is an integration platform that sits between your sales engagement tools and your CRM. Connect a sequencer on one side and HubSpot, Salesforce, Close or Attio on the other, and every email sent, opened, clicked and replied to flows into the CRM as structured contact and company records with full activity history. It matches contacts to existing records, creates new ones when needed, logs each event as a timeline activity, and syncs reply categorization so your CRM workflows can fire on prospect engagement. It is a managed integration: no custom API work, no middleware for your team to maintain.
Harris Kenny founded OutboundSync in Denver in 2023 after running Intro CRM, an outbound and CRM agency. That background shows. The product is built by someone who has lived inside HubSpot and Salesforce data models for years, and it is listed in the HubSpot App Marketplace, the Close App Marketplace and the Attio app directory.
The sequencers and LinkedIn tools it supports read like the Master Inbox integrations page: Smartlead, Instantly, EmailBison, Reply.io, Lemlist, Salesforge, Salesflow, HeyReach, Aimfox, SalesRobot, Mixmax, Clay, HotHawk and more, plus Master Inbox itself as a source.
"The OutboundSync integration brings Masterinbox's AI-powered conversation insights into Salesforce or HubSpot, syncing not just raw message history but also AI-generated sentiment analysis, intent categorization, and recommended next steps."
OutboundSync, Master Inbox integration page
Why does an outbound team need OutboundSync when it already has Master Inbox?
Because the two products answer different questions. Master Inbox answers "who replied, what did they mean, and who is handling it". OutboundSync answers "what did we send, to whom, from which campaign, and what happened next, inside the system of record".
Our HubSpot Suite puts a Master Inbox card on the contact record, syncs the conversation both ways, and lets a rep reply from HubSpot through the mailbox that received the reply. That is the right tool for a team that lives in HubSpot and wants to answer prospects there. It is not an attribution engine. It does not log every send and open as a HubSpot activity, and it does not carry sequence-level metadata into your reports.
OutboundSync does exactly that. If leadership reads a HubSpot or Salesforce dashboard to judge outbound, if you attribute pipeline to campaigns, if you build CRM workflows on opens and clicks, or if you run several sequencers into one CRM, OutboundSync is the layer that makes the numbers trustworthy. I say this to customers on calls every week: our HubSpot integration is for teams getting started with HubSpot. If you are serious about HubSpot or Salesforce reporting, use OutboundSync, and use Master Inbox for the replies.
How do Master Inbox and OutboundSync work together?
Think of it as two feeds into one CRM.
- The sequencer feed. Smartlead, Instantly, EmailBison or whichever tool you send from connects to OutboundSync as usual. Sends, opens, clicks, bounces and the replies the sequencer sees land in HubSpot or Salesforce as activities, with campaign attribution.
- The Master Inbox feed. Master Inbox reads every mailbox directly, so it also sees the replies a sequencer cannot attribute: the internal forward, the CC from an assistant, the answer from a new address, the reply that arrives three weeks after the sequence ended, the reply into a mailbox that dropped out of rotation. AI labeling puts an intent on each one. The OutboundSync integration then carries the reply, its intent and sentiment, and the thread metadata into the CRM as properties and events, one way, from Master Inbox into the record. In OutboundSync's words, the sync is "one-way, Master Inbox into your CRM", and it is in beta today. Any CRM automation you already built on OutboundSync events fires on these too.
- The rep's view. Reps work replies in Master Inbox, in Slack via Slack Send, or from the HubSpot contact card. Whichever they pick, the CRM record stays complete, because OutboundSync owns the activity log and Master Inbox only adds what the sequencer missed.
The result is a CRM that has the whole story: every touch from the sequencer, every reply including the ones that never showed up in the sequencer's inbox, and the label that says what the prospect meant.
How do you set it up?
- Connect your sequencers to OutboundSync. Do this first if you have not already. This is the feed that gives HubSpot or Salesforce the sends, opens and clicks.
- Connect Master Inbox in OutboundSync. Master Inbox is a direct integration in OutboundSync (beta, one-way into the CRM). Connect it, then choose which Master Inbox labels and AI fields you want as CRM properties.
- Build one workflow in Master Inbox. Trigger: label added. Action: send to OutboundSync. Scope it to the labels you want in the CRM, usually Interested, Meeting request, Referral, Not now and Not interested. Master Inbox workflows take two clicks; the workflows page has the builder.
- Decide who writes activities. Let OutboundSync log sends, opens and clicks. Let Master Inbox add replies and labels. Do not also push the same replies through a second HubSpot integration, or you will see duplicates on the timeline.
- Keep the HubSpot card if reps reply from HubSpot. The Master Inbox card on the contact record still works alongside OutboundSync. Replies sent from the card go out through the receiving mailbox and OutboundSync sees them like any other reply.
Onboarding is white-glove, so we connect all of this with you on the first call. Free 7-day POC. Unlimited users on every plan.
When is Master Inbox's HubSpot Suite enough, and when do you add OutboundSync?
| You want | Master Inbox HubSpot Suite | OutboundSync |
|---|---|---|
| Reply to outbound from the HubSpot contact record | Yes | No, it syncs data, reps reply elsewhere |
| The conversation and its label on the contact record | Yes | Yes, as timeline activities |
| Every send, open, click and bounce as a CRM activity | No | Yes |
| Campaign and sequence attribution in CRM reports | No | Yes |
| Salesforce | Through OutboundSync | Yes |
| Close, Attio, Pipedrive, HighLevel | Attio natively; the rest through OutboundSync | Yes, all four |
| Lemlist, Expandi, Prospeo, FindyMail, BetterContact, Icypeas, Salesflow into the CRM | Yes, through Master Inbox | Through Master Inbox |
| Replies the sequencer never saw (forwards, CC, new addresses) | Yes, that is what Master Inbox is for | Yes, once Master Inbox is connected as a source |
| Several sequencers into one CRM without duplicate contacts | Partly | Yes |
The pattern we recommend: Master Inbox for replies, OutboundSync for the CRM record. Under five clients and email only, the HubSpot Suite alone is often fine. The moment someone in the company reads an outbound report inside the CRM, add OutboundSync.
What do customers who run both say?
Several agencies on Master Inbox came to us through OutboundSync. Lance G., who runs outbound for an agency on HeyReach and EmailBison with clients on HubSpot and Salesforce, opened his first call with "I'm an OutboundSync customer, so I know you guys, I know Harris." His stack is the one this post describes: sequencers into OutboundSync, replies into Master Inbox, and a Master Inbox workflow sending labeled replies on to the CRM.
Kristopher C., who runs a HubSpot partner agency and has used HubSpot since 2016, asked whether to keep OutboundSync connected once he was on Master Inbox. The answer was yes, keep it: OutboundSync owns the HubSpot activity log, and Master Inbox adds the replies it catches. His words on Harris: "The way Harris knows HubSpot, there's no person who knows HubSpot."
Thank you, OutboundSync
"Master Inbox brings social and email conversations from many accounts into one shared workspace."
Jason Ma, OutboundSync, Partner Spotlight: Master Inbox, 24 September 2026
Partnerships in outbound are usually a logo swap. This one is a working integration that customers use every day, and a team that answers a Slack message within the hour when a record does not look right. Read their spotlight on Master Inbox, and if you are choosing a CRM sync for outbound, start at outboundsync.com.
FAQs
Do I need OutboundSync to use Master Inbox with HubSpot?
No. Master Inbox's HubSpot Suite syncs conversations and labels to the contact record and lets reps reply from HubSpot. You need OutboundSync when you want sends, opens, clicks and campaign attribution in HubSpot reporting, or when you run several sequencers into one CRM.
Do I need Master Inbox if I already use OutboundSync?
OutboundSync syncs what your sequencer sees. Forwards, CC replies, answers from new addresses and replies after a sequence ends never reach the sequencer, so they never reach the CRM either. Master Inbox reads the mailbox itself, catches those, labels them, and sends them to OutboundSync. It is also where your team works the replies: one queue across every client, views, workflows, reply agents and Slack Send.
How does Master Inbox sync to Salesforce?
Through OutboundSync, which carries replies, AI intent and sentiment and thread metadata into Salesforce one way, plus Master Inbox webhooks for replies, labels and stages. Native Salesforce sync is on the Master Inbox roadmap.
Will I get duplicate activities in the CRM?
Not if one system owns each activity type. Let OutboundSync log sends, opens, clicks and the replies it sees from the sequencer. Let Master Inbox add only the replies and labels it catches. Do not run a second HubSpot reply sync in parallel.
Which sequencers does this cover?
Any sequencer both products support: Smartlead, Instantly, EmailBison, Reply.io, Lemlist, Salesforge and Salesflow for email, and HeyReach, Aimfox and SalesRobot for LinkedIn, among others. Check the OutboundSync integrations page for the current list on their side and the Master Inbox integrations page for ours.
Is the Master Inbox integration in OutboundSync live?
It is a direct beta integration, one-way from Master Inbox into the CRM, on OutboundSync's Bronze tier. It works today; expect it to deepen.
What does OutboundSync cost?
OutboundSync sets its own pricing; see outboundsync.com. It is billed separately from Master Inbox.