I have implemented a sample Log4NetLogWriter class which internally uses log4net logging capabilities, but at the same time it can be assigned to the LogWriter property of Rebex objects because it implements Rebex.ILogWriter interface. You can download the log4net dll at the project's website. Log4net offers (among others ) a highly customizable log rolling capabilities via the RollingFileAppender class.
Here is the sample which uses the Log4NetLogWriter class. It can be used just the same as Rebex FileLogWriter with one exception. You have to configure the log4net via an app.config.
var client = new Rebex.Net.Imap();
// read the log4net configuration from app.config
// specify the verbose level you want to use
client.LogWriter = new Log4NetLogWriter("Rebex", LogLevel.Debug);
A simple rolling log writer config is available here. Just download the App.config file and put it into the Visual Studio project. The config is for 50KB rolling logs. Maximum number of log files is 100.