Does not recommend this product
Be warned, It's illegal to use a service like this to promote your products or services. It's against CAN-SPAM in the US, GDPR in the EU, PECR as well in the UK. Facilitating this is also illegal.
- Processing and tracking user personal data without informing them
- not giving them a way to opt-out.
- Hiding the details of your company
Furthermore, it would be impossible to effectively manage reputation with this system since Gmail's algorithm has over 200 data points it looks at, and looks heavily at IP, domain and sender profile. No algorithm can overcome those challenges.