Download of POPmonitor 2.1 for Mac was available from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. POPmonitor for Mac lies within Communication Tools, more precisely E-mail. We recommend checking the downloaded files with any free antivirus.
From the developer:
POPmonitor allows you to delete unwanted e-mail from your mailbox without downloading it to your computer first. And wouldn't it be a real money saver if you could trash messages with large attachments without the need to download them to your computer first
You may want to check out more software for Mac, such as Installer OS X El Capitan, which might be similar to POPmonitor.