Custom Invoice Reminder App Development

I'm looking for a web-based application that will send unpaid invoice email reminders to customers. The data for this will be manually uploaded from Excel sheets.

Key Requirements:
- Web-based platform
- Manual upload of Excel data
- Use of a custom SMTP server for sending emails

Ideal Skills and Experience:
- Experience in web application development
- Familiarity with handling Excel data uploads
- Knowledge of integrating and configuring custom SMTP servers
- Strong attention to detail and reliability

Please provide examples of similar work done. Looking forward to your bids!