> For the complete documentation index, see [llms.txt](https://docs.growsurf.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.growsurf.com/integrations/resend.md).
# Resend
## Sync participants to a Resend Segment
**Step 1:** In [Resend > API Keys](https://resend.com/api-keys), create a new API key with *Full Access* (this permission is required so GrowSurf can read Segments and manage Contacts and Contact Properties).
**Step 2:** In GrowSurf, open *Program Editor > 4. Options > Integrations > Resend*. Enter the API key, then connect your account.
Connect Resend with a Full access API key.
**Step 3:** Select the Resend Segment that should receive GrowSurf participants, then save your changes. GrowSurf creates the Contact Properties listed below and starts syncing new and updated participants.
Select the Resend Segment that should receive participant data.
{% hint style="warning" %}
Connect Resend before importing participants. If participants are already in your Program, follow [these ESP sync options](https://support.growsurf.com/article/385-how-can-i-sync-my-growsurf-participants-to-my-esp) to send their GrowSurf data to Resend.
{% endhint %}
## Contact Properties
GrowSurf creates these account-level Contact Properties in Resend. Use them in Broadcasts with Resend's `{{{contact.property_name}}}` syntax.
| Contact Property | Property key | Type | Description | Example |
| ---------------------------------------- | ---------------------------------- | ------ | ------------------------------------------------------------------- | -------------------------------------- |
| GrowSurf Share URL | `grsf_share_url` | String | The participant's unique referral link | `https://growsurf.com?grsf=abc123` |
| GrowSurf Participant ID | `grsf_participant_id` | String | The participant's GrowSurf ID | `abc123` |
| GrowSurf Referral Status | `grsf_referral_status` | String | The participant's referral-credit status | `CREDIT_PENDING` |
| GrowSurf Participant First Name | `grsf_participant_first_name` | String | The participant's first name | `Bob` |
| GrowSurf Participant Last Name | `grsf_participant_last_name` | String | The participant's last name | `Loblaw` |
| GrowSurf Referrer First Name | `grsf_referrer_first_name` | String | The referrer's first name, when applicable | `Gavin` |
| GrowSurf Referrer Last Name | `grsf_referrer_last_name` | String | The referrer's last name, when applicable | `Belson` |
| GrowSurf Referrer Email | `grsf_referrer_email` | String | The referrer's email, when applicable | `gavin@example.com` |
| GrowSurf Total Referral Count | `grsf_total_referral_count` | Number | The participant's all-time referral count | `12` |
| GrowSurf Monthly Referral Count | `grsf_monthly_referral_count` | Number | The participant's referral count for the current month | `3` |
| GrowSurf Previous Monthly Referral Count | `grsf_prev_monthly_referral_count` | Number | The participant's referral count for the previous month | `8` |
| GrowSurf Next Milestone | `grsf_next_milestone` | String | The next milestone message, when the Program uses milestone rewards | `2 referrals until your next reward` |
| GrowSurf Next Monthly Milestone | `grsf_next_monthly_milestone` | String | The next monthly milestone message, when applicable | `1 referral until this month's reward` |
| GrowSurf Total Invite Count | `grsf_total_invite_count` | Number | The participant's all-time invite count | `24` |
| GrowSurf Total Impression Count | `grsf_total_impression_count` | Number | The participant's all-time referral-link view count | `150` |
The referral status can be `CREDIT_PENDING`, `CREDIT_AWARDED`, or `CREDIT_EXPIRED`.
[View the Resend tutorials](/integrations/resend/tutorials.md) for copy-and-paste examples. View Resend's [Contact Properties guide](https://resend.com/docs/dashboard/audiences/properties) to see how properties work in Broadcasts.
## Troubleshooting
* If GrowSurf cannot connect, confirm the API key has Full access. Sending-only keys cannot read Segments or manage Contacts.
* If the selected Segment was deleted, choose an existing Segment in GrowSurf and save again.
* Check the GrowSurf participant's activity logs when a participant does not sync. GrowSurf retries temporary provider errors for up to seven days.
---
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