Python Developer Needed for Email Sending Desktop Software (Inbox Delivery Focus)

I am looking for an experienced Python developer to create a desktop application that can send emails through a normal Gmail account using Google OAuth authentication.

Key Focus: Emails must land in the inbox, not in spam.

Requirements

• Build a lightweight Python desktop app (cross-platform preferred: Windows/Mac/Linux)
• Use Gmail SMTP with OAuth 2.0 (no plain password authentication)
• Ability to upload contact lists (JSON, CSV)
• Allow writing Subject, Body (HTML/Text), Attachments (including HTML to PDF)
• Schedule email sending by selecting date/time
• Ensure maximum inbox delivery rate (avoid spam triggers)

Ideal Skills:

• Python (desktop apps: Tkinter, PyQt, etc.)
• Email deliverability best practices
• Gmail API / Google OAuth 2.0
• SMTP email sending
• Email scheduling and attachment handling
• Packaging app for easy install (optional: make runnable with CMD/terminal)

Bonus Skills:

• Knowledge of DKIM/SPF
• Lightweight UI/UX design

Notes:

We are facing issues where emails are going into spam — you must understand how to authenticate properly and optimize headers/content for Gmail inbox delivery.

Budget: Open to offers.

Start Date: Immediate.