Mailgo in Magento 2
Mailgo for Magento 2 extension (no longer maintained)
GitHub (no longer maintained)
Mailgo Magento 2 is available on GitHub. However, unfortunately, it is no longer maintained.
https://github.com/manzinello/magento2-mailgo (archived repository)
Composer / Packagist (no longer maintained)
Mailgo for Magento con be installed also through Composer / Packagist. However, unfortunately, it is no longer maintained.
About Magento Marketplace
Mailgo is no longer present on Magento Marketplace, you can install Mailgo on Magento 2 through Packagist or directly downloading it from GitHub (archived repository).