Refresh unlimited POP3 email accounts of Gmail with a frequency of one minute for free.
This is chrome extension but if you use other browser you can use with Tampermonkey : https://gist.github.com/Ayce45/4e8bbf6c1c3e3b07d3c5af891ad4a7bb
It's simple you need to install the extension Tampermonkey in other browser and click to "add new script" and paste the gist. Open the good URL like with the chrome extension (https://mail.google.com/mail/u/0/#settings/accounts) and it's work.