In the IMAP Email Content Integration you can specify a folder to check, however if a folder has a name with an “@” as the first character it tells you there is an error.
There is a good reason to use the “@” as the first character in a folder name, most programs will do an alpha sort of folder names, this is a problem if you have an important folder you want at the top but it starts with a letter near the end of the alphabet (example “receipts”). If you change “receipts” to “@receipts” it will now be alpha sorted to the top of the list. If you have a few “@” folders you can use “@@” to force that folder to be at the top.
Using “@” folder prefix has been a productivity tool that’s been around for years, David Allen author of Getting Things Done recommends using this.