Debug Thunderbird Addon -- 2

I'm looking for a skilled developer to debug my Thunderbird addon. The addon is supposed to send emails silently via an experiment API, but currently, it's not functioning as intended.

Requirements:
- Fix the issue causing the error message when sending emails
- Ensure the addon can send emails without any errors
- Add a bit of extra features. The addon is already 80% completed

Ideal Skills and Experience:
- Experience with Thunderbird addons
- Strong debugging skills
- Familiarity with email APIs and authentication