How to auto backup a Gmail account to a QNAP NAS

It’s pretty straightforward to (incrementally) backup all emails in a Gmail account to a QNAP NAS. There’s a QNAP NAS solution using Getmail but it comes with some limitations. I prefer to use Gmail-Backup. It doesn’t need any configuration files and it doesn’t have a 100 messages per session limit. It stores all mails in …