curl -X POST "https://server.smartlead.ai/api/v1/campaigns/123/reply-email-thread?api_key=YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "email_stats_id": "abc-123",
    "email_body": "Thanks for your interest! Let me know if you have any questions.",
    "add_signature": true
  }'

import requests

def reply_to_lead(campaign_id, email_stats_id, body, add_signature=True):
    payload = {
        "email_stats_id": email_stats_id,
        "email_body": body,
        "add_signature": add_signature
    }
    
    response = requests.post(
        f"https://server.smartlead.ai/api/v1/campaigns/{campaign_id}/reply-email-thread",
        params={"api_key": "YOUR_API_KEY"},
        json=payload
    )
    
    if response.status_code == 200:
        print("✅ Reply sent")
    
    return response.json()

reply_to_lead(123, "abc-123", "Happy to help! Let me know your questions.")

{
  "success": true,
  "message": "Reply sent successfully"
}