Singlebox 38.2 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.
According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The software lies within Communication Tools, more precisely Texting & Video calls. The actual developer of this free Mac application is WebCatalog Ltd.
From the developer:
Singlebox for Mac is an all-in-one messaging and e-mailing app. It gathers in a single place all your web services and accounts, including Discord, WhatsApp, Messenger, Slack, Telegram and many many more. Singlebox allows you to add each service many times. This makes Singlebox the perfect tool to manage multiple business and private accounts all at the same time. You could even use five different Messenger or Slack accounts at once if desired.
You may want to check out more Mac applications, such as Linkinus, Blink or Psi, which might be related to Singlebox.