Reliable SMTP Configuration for OpenSign

As the owner of a Digital Ocean hosted OpenSign Open Source app, I need an expert to configure SMTP settings for both sending and receiving emails. The most critical aspect of this project is reliability, as the application needs to maintain a high level of uptime and deliverability for the emails.

Key tasks and requirements include:
- Configuring SMTP settings for OpenSign and ensuring seamless integration with third-party mail tools like Mailgun.
- Ensuring the setup is optimized for both sending and receiving emails efficiently and reliably.
- Providing guidance on best practices for maintaining a secure and cost-efficient email system.

Ideal candidates for this project should have:
- Proven experience in configuring SMTP settings for web applications.
- Expertise in working with third-party mail tools like Mailgun.
- A strong understanding of email delivery best practices and a track record of ensuring reliability.
- Excellent communication skills to guide us through the process and provide recommendations for future maintenance.

Please note that I do not require assistance with setting up DNS records for email authentication; this is already configured.