Breaklines are used to truncate text in incoming emails. This is useful when emails from users contain a lot of repeated content in the form of ticket history. You can edit breaklines from: Admin CP -> Email Parser -> Breaklines.
In addition, you'll need to insert breaklines at the top of your templates. The templates concerned are:
NOTE: If you have multiple template groups, you will need to do this for each one of them.
For detailed instructions on using breaklines, refer to the following User Guide article: https://classic.kayako.com/article/809