Modify Wildduck Email Server

I need a modification to the Wildduck email server. The goal is to allow emails to be received at non-existent addresses before user accounts are created.

Requirements:
- Emails can be sent to any address on my domain (for example, myemail.com) even if the user doesn't exist yet, and a temporary account is created upon receiving of first email.
- Emails for these non-existent users are stored until the account is created.
- When a user registers, if a temporary account exists, they will just set a password to access the stored emails.
- User accounts are still required to send emails from these addresses.
- Temporary user accounts should be kept indefinitely if not registered.
- No need for verification, just username and password.
- Storage limits should remain unchanged from the original Wildduck implementation.

Ideal Skills and Experience:
- Experience with email server management, specifically Wildduck.
- Strong understanding of Node.js and MongoDB (Wildduck's tech stack).
- Ability to modify existing codebases and implement new features.
- Familiarity with handling temporary user accounts and email storage.

Please share examples of similar work done.