Real-time
Two-way sync
Changes in Apollo.io or Resend instantly reflect in both systems. No stale data, no manual imports.
CRM ⇄ Business productivity
Apollo.io to Resend integration — real-time, two-way sync
Keep Apollo.io and Resend in sync without custom scripts. Cut weeks of integration work, eliminate silent data drift, and give your team a single, reliable source of truth.
- SOC 2 and 6 other compliance frameworks
- POC with real engineers in minutes
Adopted by fast-scaling companies moving mission-critical data in real time
Case study
Migrated from MuleSoft
Case study
Migrated from Celigo
Migrated from Heroku Connect
Migrated from Matillion
Case study
Migrated from Fivetran
Case study
Migrated from Celigo
Why teams connect Apollo.io and Resend
Sync what happens in Resend with the customer records in Apollo.io, in real time and in both directions.
The CRM is supposed to be the record of every customer relationship, but customer-relevant information also accumulates in the other tools a team runs. Whatever Resend holds or produces that touches a customer, whether conversations, payments, replies, enriched data, or notes, the CRM only benefits if it arrives without someone copying it over.
Stacksync connects Domains, Email events, API keys, Emails in Resend to Deals (Opportunities), Tasks and calls, Custom fields, Contacts in Apollo.io with bi-directional, real-time sync. Activity and record changes in Resend update the matching contact or account in Apollo.io, and CRM data flows the other way wherever Resend can store and use it.
Common use cases
- 01 Keep suppression and unsubscribe state synced between Resend and other marketing tools to stay compliant.
- 02 Feed open and click events into a warehouse for engagement analytics alongside product data.
- 03 Push CRM opportunity stages back into Apollo so reps see pipeline context while sequencing.
- 04 Land sequence enrollment status and outcomes in a warehouse for outbound performance reporting.
Common sync patterns
Where Resend runs outreach
Prospects, sends, and replies sync into Apollo.io, keeping lead status current without manual imports.
Where Resend supplies contact or company data
Enriched fields land directly on records in Apollo.io, and refreshes keep them from going stale.
Where Resend can store CRM context: fields kept current
Owner, lifecycle stage, or account details from Apollo.io sync into Resend, so people working there have the context without switching tools.
What you can sync between Apollo.io and Resend
Representative objects on each side — any object or custom field can map to any target. Schemas are auto-detected; types are converted between the two systems.
| Apollo.io objects | Resend objects | How this pairing syncs | |
|---|---|---|---|
| Contacts People saved to your Apollo account, synced with emails, phone numbers, and enrichment fields. | Contacts Recipient records with email, name, and subscription state, synced from CRMs or databases. | Same entity on both sides — records pair one-to-one and field-level changes reconcile in both directions. | |
| Tasks and calls Rep activity records synced for activity reporting and coaching workflows. | API keys Scoped credentials managed per environment for send and read access. | Tasks and calls is specific to Apollo.io and API keys to Resend — each maps to any object or custom field on the other side. | |
| Custom fields Account- and contact-level custom attributes mapped field-by-field in a sync. | Emails Sent messages retrievable by ID with current delivery status. | Custom fields is specific to Apollo.io and Emails to Resend — each maps to any object or custom field on the other side. | |
| Accounts Company records with firmographic attributes, matched to CRM accounts during sync. | Audiences Named contact lists that broadcasts target; typically mirrored from CRM segments. | Accounts is specific to Apollo.io and Audiences to Resend — each maps to any object or custom field on the other side. | |
| People (database records) Prospects from Apollo's global database, pulled into downstream systems once enriched or saved. | Broadcasts One-to-many campaign sends addressed to an audience. | People (database records) is specific to Apollo.io and Broadcasts to Resend — each maps to any object or custom field on the other side. | |
| Sequences Outreach cadences (emailer campaigns in the API); enrollment status is read to track which contacts are being worked. | Domains Verified sending domains with DNS and DKIM status. | Sequences is specific to Apollo.io and Domains to Resend — each maps to any object or custom field on the other side. |
How changes propagate between Apollo.io and Resend
Each direction of the sync is driven by what the source system can signal and what the destination accepts — detection, delivery, and expected latency below.
Apollo.io Resend Interval-based propagation
DetectionStacksync polls Apollo.io for changes on an incremental schedule, reading only records changed since the previous pass. Polling on updated-at timestamps.
DeliveryEach detected change is written to Resend through its API, with automatic retries and rate-limit backoff.
Resend Apollo.io Sub-second propagation
DetectionResend notifies Stacksync of record changes through webhook events. Webhooks for email lifecycle events.
DeliveryEach detected change is written to Apollo.io through its API, with automatic retries and rate-limit backoff.
Rate-limit considerations
- Apollo.io: Rate limits and enrichment credits vary by plan; bulk endpoints are throttled separately from single-record calls.
What ships with Apollo.io ⇄ Resend
Connect Apollo.io and Resend for flexible, real-time data sync.
Real-time sync, workflow automation, event queues, EDI, and monitoring, for every Apollo.io–Resend connection.
No-code + pro-code
Workflow automation
Trigger automated workflows whenever Apollo.io or Resend data changes, update records, fire webhooks, or kick off sequences without brittle API scripts.
At scale
Event queues
Handle millions of events per minute without losing a single Apollo.io or Resend record.
Observability
Monitoring
Track your Apollo.io ⇄ Resend sync health, view errors, and replay failed events in one click.
Trading partners
EDI
Transform legacy EDI complexity into simple database interactions between Apollo.io and Resend.
How the Apollo.io and Resend connectors work
Apollo.io
- Integration surface
- REST API
- Authentication
- API key (passed in request headers); master keys unlock account-wide endpoints
- Change detection
- Polling on updated-at timestamps; webhook callbacks exist only for delivering asynchronous enrichment results, not as a general change-event stream
- Capabilities
- read · write
- Rate limits
- Rate limits and enrichment credits vary by plan; bulk endpoints are throttled separately from single-record calls
Resend
- Integration surface
- REST API
- Authentication
- API key (Bearer token)
- Change detection
- Webhooks for email lifecycle events; polling for contact and audience state
- Capabilities
- read · write · webhooks
How it works
How to connect Apollo.io to Resend — three steps, no code
Configure and sync within minutes, no code. Whether you sync 50k or 100M+ records, Stacksync handles the queues, infra, and plumbing. Integrations are non-invasive and need zero setup on your systems.
- 01
Connect your apps
Authenticate Apollo.io and Resend with each platform's native method — OAuth, API keys, or service accounts — plus secure options like SSH tunneling, IP whitelisting, and VPC peering.
Apollo.io
connected
Resend
connected
OAuth 2.0SSH tunnelSSL certificateVPC peering - 02
Choose tables
Pick the Apollo.io and Resend objects to sync — Stacksync auto-detects both schemas, including custom fields where the platform exposes them. Sync to existing tables, or let Stacksync create new ones with ideal data types.
objects · Apollo.io ⇄ ResendCustomers 12,480Sales Orders 8,213Invoices 5,902Items 1,344 - 03
Map fields
Fields map automatically even when names and types differ. Stacksync handles transformation and type casting for you, zero configuration required.
Apollo.io ResendCompany company_name textEmail email textAmount amount numericCreated created_at timestamp
FAQ
Apollo.io and Resend integration FAQ
-
Yes. Stacksync provides a managed, real-time two-way integration between Apollo.io and Resend: authenticate both systems, choose the objects to sync (such as Apollo.io's Contacts and Tasks and calls), map fields visually, and changes propagate both ways in milliseconds — no code required.
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Stacksync is SOC 2 Type II and ISO 27001 certified with HIPAA BAA support. Data is encrypted in transit, and a zero-persistent-storage architecture means Apollo.io and Resend records are not retained after a sync operation.
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Stacksync pricing is usage-based and starts at $1,000/month, including the managed Apollo.io and Resend connectors, real-time two-way sync, monitoring, and support. That replaces building and maintaining a custom Apollo.io–Resend integration in-house.
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Yes — Stacksync ships production-grade connectors for both Apollo.io and Resend. The connectors handle authentication, schema detection, rate limits, and retries; you configure the sync, and Stacksync operates it.
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Change detection on Apollo.io: Polling on updated-at timestamps; webhook callbacks exist only for delivering asynchronous enrichment results, not as a general change-event stream. On Resend: Webhooks for email lifecycle events; polling for contact and audience state. Each detected change propagates to the other side in milliseconds, with field-level conflict resolution and an inspectable event log.
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On the Resend side: Domains, Email events, API keys, Emails, plus custom fields where Resend exposes them. On the Apollo.io side: Deals (Opportunities), Tasks and calls, Custom fields, Contacts. Stacksync auto-detects both schemas and converts types between the two systems.
SECURITY
Security teams trust Stacksync
As a data company, we understand the importance of keeping your data secure. Stacksync is built with security best practices to keep your data safe at every layer, and is DPF-certified for US, EU, UK and CH data transfers.
SOC 2 Type II
ISO 27001
HIPAA BAA
GDPR
CCPA
DPF US-EU-UK-CH
→ SECURITY WITH BENEFITS
SSO & SCIM
Let your users access Stacksync from your centralized user management systems. Works with Okta, Azure, Google SSO and more.
Alerts
Immediately get alerted about record syncing issues over email, Slack, PagerDuty and WhatsApp. Resolve issues from a centralized dashboard with retry and revert options.
Secure connection options
Securely connects to your systems with:
Related integrations
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