Automated Email Follow-up

Create a robust Python script to automate the initial follow-up emails to new leads. The script should be well-commented so I can understand each part.

Core Functionality:

Data Source: The script must read new lead information from a CSV file named leads.csv. The CSV will have the following columns: lead_id, first_name, email_address, and inquiry_topic.

Email Logic: The script needs to send a unique email for each inquiry_topic. Create three distinct email templates for the following topics:

"Service Pricing"

"Product Demo"

"General Question"

Personalization:

The greeting of each email must be personalized using the lead's first_name.

The subject line should be dynamic, incorporating the specific inquiry_topic.

Tracking: To prevent sending duplicate emails, the script must track which leads have already been contacted. After successfully sending an email, it should record the lead_id in a separate file named sent_leads.txt.

Configuration: The script should have a clear section at the top for configuration, including placeholders for SMTP server details (host, port) and email credentials (username, app password).

Could you provide a complete Python script that accomplishes this?