API Logs

The Logs page provides detailed information about every API request made to Lettr, helping you monitor activity, debug integrations, and troubleshoot issues quickly.

Overview

Access your logs from the Logs page in the dashboard. The API Logs view shows a comprehensive table of all API requests with the following information:

Column	Description
Timestamp	When the request was made
Method	The HTTP method used (GET, POST, DELETE, etc.)
Path	The API endpoint called (e.g., `api/emails`, `api/domains`)
Status	The HTTP response status code
IP Address	The IP address that made the request
API Key	Which API key was used (if applicable)
Details	Click to view full request and response details

API logs are retained for 30 days. After this period, logs are automatically deleted.

Filtering Logs

Use the filter controls at the top of the page to narrow down your search.

Date Range

Select a custom date range to view logs from a specific period. The default view shows the last 7 days.

API Keys

Filter logs by specific API key to see requests made by a particular integration:

All API Keys - View logs from all API keys
Specific key - Select a named API key to filter

This is useful when debugging a specific integration or tracking usage per application.

User Agents

Filter by the SDK or client used to make requests:

User Agent	Description
SMTP	Requests via SMTP relay
Node.js	Lettr Node.js SDK
PHP	Lettr PHP SDK
Python	Lettr Python SDK
Ruby	Lettr Ruby SDK
Go	Lettr Go SDK
Rust	Lettr Rust SDK
Java	Lettr Java SDK
.NET	Lettr .NET SDK
cURL	Direct cURL requests
Other	Other HTTP clients

Status Codes

Filter by HTTP response status to quickly identify successful requests or errors:

Status	Description
All Statuses	Show all requests
200 - Ok	Successful GET requests
201 - Created	Successful POST requests (resource created)
400 - Bad Request	Invalid request format or parameters
401 - Unauthorized	Missing or invalid API key
403 - Forbidden	API key lacks required permissions
404 - Not Found	Requested resource doesn’t exist
422 - Unprocessable Content	Request validation failed
429 - Too Many Requests	Rate limit exceeded
451 - Unavailable For Legal Reasons	Content blocked for legal compliance
500 - Internal Server Error	Server-side error

To quickly find failed requests, filter by 4xx and 5xx status codes. This helps you identify integration issues that need attention.

Searching Logs

Click the Search button after applying filters to refresh the results. The search respects all active filters including date range, API key, user agent, and status code selections.

Log Details

Click the details icon (or anywhere on a row) to open the full log detail view for any request.

Request Information

The detail view shows:

Method & Path - The HTTP method and API endpoint (e.g., POST api/emails)
Status Code - The response status with color indicator (green for success, red for errors)
Timestamp - Exact date and time of the request
Request Body - The full JSON payload sent to the API

Example request body:

{
  "from": "sender@example.com",
  "to": [
    "recipient@example.com"
  ],
  "subject": "Test send",
  "text": "Plain-text body",
  "html": "<p>HTML body</p> And click here: <a href=\"https://example.com\">Link</a>"
}

Response Information

Response Body - The complete API response

Example response body:

{
  "message": "Email queued for delivery.",
  "data": {
    "request_id": "759976368330071843",
    "accepted": 1,
    "rejected": 0
  }
}

Metadata

Additional information about the request:

IP Address - The source IP address
API Key - The API key name used (with the key itself partially masked for security)
User Agent - The client or SDK used (e.g., bruno-runtime/3.0.2, lettr-node/1.0.0)

Truncated Fields

To optimize storage and display, some large fields are truncated in the logs:

Field	Behavior
HTML body	Truncated after 200 characters
Plain text body	Truncated after 200 characters
AMP HTML body	Truncated after 200 characters
Attachments	Replaced with item count (e.g., “3 items”)
Metadata	Replaced with item count (e.g., “2 items”)
Substitution Data	Replaced with item count (e.g., “4 items”)

Truncation only affects log display. The actual email sent contains the full content.

Common Status Codes

Success Codes

Code	Meaning	Typical Cause
200	OK	GET request successful
201	Created	POST request successful, resource created

Client Error Codes

Code	Meaning	How to Fix
400	Bad Request	Check request body format and required fields
401	Unauthorized	Verify your API key is correct and active
403	Forbidden	Check API key permissions for this endpoint
404	Not Found	Verify the resource ID exists
422	Unprocessable	Check validation errors in response body
429	Too Many Requests	Implement rate limiting, wait before retrying
451	Legal Block	Content flagged for compliance reasons

Server Error Codes

Code	Meaning	What to Do
500	Internal Error	Retry the request; contact support if persistent

Troubleshooting with Logs

Finding Failed Requests

Set the Status filter to show only error codes (4xx, 5xx)
Click Search to filter results
Click on a failed request to view details
Check the Response Body for error messages

Debugging a Specific Integration

Filter by the API Key used by that integration
Optionally filter by User Agent if using an SDK
Review recent requests for patterns or errors

Tracking Rate Limit Issues

Filter by status code 429 - Too Many Requests
Note the timestamps to identify when limits are being hit
Review the IP addresses to see if requests are distributed
Implement exponential backoff in your integration

Best Practices

Monitor Regularly

Check your API logs periodically to catch issues early:

Watch for error patterns — A sudden spike in 422 or 401 errors often indicates a configuration change or integration bug
Set up alerting — Use webhook-based alerting so your team is notified when error rates exceed a threshold
Monitor rate limits — Pay particular attention to 429 errors, which may signal that your integration needs pacing improvements or a plan upgrade

Use Descriptive API Key Names

Name your API keys descriptively (e.g., “Production Server”, “Staging Environment”, “Marketing Integration”) to easily identify which system made each request.

Correlate with Email Events

When troubleshooting email delivery issues:

Find the send request in logs using the timestamp
Note the request_id from the response
Use this ID to track the email in the Emails dashboard

Next Steps

API Keys

Manage your API keys and permissions

Rate Limits

Understand and handle rate limits

Documentation

Quickstart

Learn

Integrations

Resources

Overview

Filtering Logs

Date Range

API Keys

User Agents

Status Codes

Searching Logs

Log Details

Request Information

Response Information

Metadata

Truncated Fields

Common Status Codes

Success Codes

Client Error Codes

Server Error Codes

Troubleshooting with Logs

Finding Failed Requests

Debugging a Specific Integration

Tracking Rate Limit Issues

Best Practices

Monitor Regularly

Use Descriptive API Key Names

Correlate with Email Events

Next Steps

API Keys

Rate Limits

​Overview

​Filtering Logs

​Date Range

​API Keys

​User Agents

​Status Codes

​Searching Logs

​Log Details

​Request Information

​Response Information

​Metadata

​Truncated Fields

​Common Status Codes

​Success Codes

​Client Error Codes

​Server Error Codes

​Troubleshooting with Logs

​Finding Failed Requests

​Debugging a Specific Integration

​Tracking Rate Limit Issues

​Best Practices

​Monitor Regularly

​Use Descriptive API Key Names

​Correlate with Email Events

​Next Steps

API Keys

Rate Limits

Overview

Filtering Logs

Date Range

API Keys

User Agents

Status Codes

Searching Logs

Log Details

Request Information

Response Information

Metadata

Truncated Fields

Common Status Codes

Success Codes

Client Error Codes

Server Error Codes

Troubleshooting with Logs

Finding Failed Requests

Debugging a Specific Integration

Tracking Rate Limit Issues

Best Practices

Monitor Regularly

Use Descriptive API Key Names

Correlate with Email Events

Next Steps