Enhances the default OpenCart mailing behavior by introducing a new option that targets only customers who have placed at least one order, excluding users who are simply registered without purchases.
By default, OpenCart pulls emails from the customer table, which means:
✔ Includes: all registered customers
❌ Does NOT require any completed orders

What this modification does

- Adds a new admin dropdown option: “Customers with at least one order”
- Modifies the send() function to: Fetch only customers with ≥1 order, Exclude registered-only users, Remove duplicate emails using array_unique()

Result
-Clean, relevant recipient list
-Targets actual buyers instead of inactive accounts
-Works as expected even when no product filter is applied

Creates a log file
system/storage/logs/marketing_mail_sent.log
Each entry includes:
timestamp | recipient email | subject

Provides a quick and reliable way to confirm exactly which emails were sent.