Marketing Automation · Integration
Reply.io
Add Reply.io to your product for your customers, and give your AI agents governed access to it.
Reply.io's core objects are people, or prospects, and campaigns made of sequenced steps, with the API key passed in its own header rather than as a bearer token. The constraint that shapes every integration is that a prospect can be active in only one campaign at a time, so adding someone to a second sequence fails until they are paused or removed from the first, and the remove call is a separate endpoint from the add. Adding a prospect and pushing them into a campaign is a single combined operation in the v1 API, which is not obvious from the resource list. Replies detected on an email automatically stop the remaining steps for that prospect, so your own records will drift unless you read status back rather than assuming a sequence ran to completion. fastn holds each customer's Reply key, keeps prospect writes scoped to their own workspace, and manages credential upkeep as keys change.
In your product
Embedded for your customers. Per-tenant auth, no per-customer code, maintained by fastn.
Let a customer connect their own Reply.io account so outreach runs from their sending identities
Push qualified leads from your product straight into the right campaign with mapped custom fields
Read per-prospect step and reply status back into your records so owners see where outreach stands
Pause or remove a prospect from sequences automatically when they convert or opt out in your product
For your AI agents
Governed, audited access for the agents you build, through the MCP server.
Let an agent add prospects only to approved campaigns and never create or edit campaign steps
Have an agent check whether a contact is already in an active sequence before any outreach is queued
Audit per tenant which prospects an agent pushed, to which campaign, and which it removed
Example prompt
Is this lead already in an active Reply.io campaign, and has anyone replied to the last sequence step?
Set up Reply.io in 4 steps
- 01Enable the Reply.io connector from your fastn dashboard.
- 02Have each customer authorise their own Reply.io account, so calls run under their credentials rather than a shared key.
- 03Decide which campaigns, segments and subscribers your product needs, map those fields, then enable the actions and triggers you want.
- 04Call it from your product and expose it to your agents through the same governed connection.
Why teams use the Reply.io integration
What you get by embedding it with fastn instead of building it yourself.
- Ship a Reply.io integration without building it. Your customers connect their own Reply.io account inside your product and work their campaigns, segments and subscribers there, with no per-customer code on your side.
- Handle the part that actually costs time: engagement data arrives as a high-volume event stream, so ordering and deduplication matter. fastn owns the auth, token refresh, rate limits, pagination and breaking-change fixes, so a Reply.io update is not your on-call problem.
- One integration serves your product and your agents. The same governed Reply.io connection powers in-product features and gives AI agents scoped, audited access, so you trigger and measure campaigns from inside your product without wiring it twice.
Used by these teams
Compare with
Mailchimp
Marketo
Google AdsOften used alongside
Tools the same teams tend to run next to Reply.io, across other categories.
Salesforce
HubSpot
Pipedrive
Zoho CRMReply.io integration FAQ
How do I add a Reply.io integration to my product?
Enable the Reply.io connector in your fastn dashboard, then let each customer authenticate their own Reply.io account. fastn handles the OAuth flow, token storage and refresh per tenant, so there is no Reply.io client code in your app and no per-customer branch in your codebase. Setup is 4 steps.
Do my customers each connect their own Reply.io account?
Yes. Every connection is scoped to the individual customer, so each authorises their own Reply.io account and only ever sees their own campaigns, segments and subscribers. That per-tenant isolation is the point of an embedded integration: you support the long tail of customer setups without maintaining an integration per customer.
Can AI agents use this Reply.io integration?
Yes. The same connection is exposed to your agents through the fastn MCP gateway, with permissions scoped per tenant and every call audited. Let an agent add prospects only to approved campaigns and never create or edit campaign steps
Who maintains the Reply.io integration?
fastn does. When Reply.io changes an endpoint, deprecates a field or alters its auth, the fix lands in the connector rather than in your backlog, and your customers' connections keep working.
Can I trigger a Reply.io campaign from an event in my product?
Yes. Product events can start a campaign, add a contact to a segment, or enrol someone in a journey, so lifecycle messaging follows what a user actually did rather than a nightly export.
Can I read engagement results back from Reply.io?
Yes. Results come back scoped per tenant, so your product can act on them without one customer's data mixing with another's. What you get depends on the channel: opens, clicks, bounces and unsubscribes where there are sends, and impressions, spend and conversions where there are campaigns.
What can I build with the Reply.io integration?
A common starting point: let a customer connect their own Reply.io account so outreach runs from their sending identities. Teams also use it for the other use cases listed above, and expose it to agents for governed reads and writes.
How much does the Reply.io integration cost?
It is included. Pricing is based on connected accounts, not on how many connectors you enable, so adding Reply.io does not change your per-connector cost. You can start free with 3 connected accounts.
Add Reply.io to your product
Start free with 3 connected accounts. No sales call required, and no per-customer integration code.