Simple Notes for Gmail 2.7.1.9 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. This free Mac app was originally developed by Bart Solutions Limited. The software lies within Internet & Network Tools, more precisely Browser extensions.
From the developer:
Simple Notes for Gmail helps you add notes to e-mail threads with ease in Gmail and Inbox. The application allows you to add notes to individual Gmail conversations, store notes in your own Google Drive, and show abstracts in the e-mail summary . The tool supports multiple Gmail accounts in the same browser.
You may want to check out more Mac applications, such as Simple Notes, Simple or MailTab Pro for Gmail, which might be similar to Simple Notes for Gmail.
Document management
E-mail Tools