> ## Documentation Index
> Fetch the complete documentation index at: https://flywheel.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# One-to-One Email
> Send a builder-defined one-to-one email while letting the agent choose timing and recipient
## How One-to-One Email works
**One-to-One Email** sends a personal email from a configured team member sender using content defaults you define in the builder. Unlike marketing emails, these messages appear as direct communication from a real person on your team, making them ideal for relationship-driven outreach.
The builder controls the sender identity, subject, and body content, while the agent handles timing and recipient selection during the run. This ensures every one-to-one message maintains a consistent, personal tone while still being triggered automatically based on user behavior or lifecycle stage.
## Configuration
Instructions for when and how the agent should use this tool.
Target user (`params.to_id`), with user or agent assignment mode.
Team member sender (`params.from_id`) used as the one-to-one sender.
Optional CC emails.
Optional BCC emails.
Controls whether the run continues when send fails.
The status of the email send operation. Can be `success`, `failure`, or `skipped`.
The ID of the user that the email was sent to.
The team member ID used as the sender for this email.
The ID of the email that was sent (available on success).
The options used when creating the email, including subject, body, CC, and BCC settings (available on success).
The response from the email creation service (available on success).
The code indicating why the email send operation failed or was skipped. Can be `resend_error`, `duplicate_email`, or `user_marketing_email_opt_out`.
The message of the error that occurred (available on failure).
## Use cases
**Lifecycle Handoff**
```
Condition: User passes qualification criteria and is assigned a CSM
Action: Send one-to-one introduction note from the assigned CSM
Outcome: New qualified user receives a personal welcome from their point of contact
```
**Churn Risk Outreach**
```
Condition: Account risk score crosses a critical threshold
Action: Send curated outreach message from the account owner
Outcome: At-risk user receives direct, personal communication to re-engage
```
**Missed Milestone Check-In**
```
Condition: User has not completed a key onboarding step after 10 days
Action: Send one-to-one reminder from the success lead with guidance
Outcome: Stalled user receives targeted help to get back on track
```
**Renewal Conversation Starter**
```
Condition: User subscription renewal is within 30 days
Action: Send personal note from account manager to open renewal discussion
Outcome: Proactive relationship touch before the renewal window closes
```
## Best practices
**Sender Identity**
* Map the sender to the team member who actually owns the relationship with the recipient.
* Avoid using generic or shared sender identities — one-to-one emails should feel personal.
* Use `from_id` output to verify the correct sender was used in each delivery.
**Delivery and State Tracking**
* Follow successful sends with Set Custom Property to mark that outreach has been completed.
* Enable `complete_on_send_failure` when the agent run should proceed regardless of email delivery status.
* Monitor `code` output values like `duplicate_email` to prevent repeat outreach to the same user.
**Content and Template Quality**
* Keep email content defaults up to date and aligned with your team's current voice and messaging.
* Review templates regularly to ensure they reflect current product state and company positioning.
* Use preview text to reinforce the subject line and improve open rates in recipient inboxes.