After having a configuration issue on my SonicWall server for a couple years, I had run up over 20,000 email alerts under the monitoring section of SonicWall’s administration page. One of their techs told me that I should be able to simply delete the Alert CSV files from \Program Files\MailFrontierEG\data\reports\
He couldn’t guarantee that it wouldn’t cause some “weirdness” with the reports however, but he thought that if I rebuilt the reports, that would clear things up. Only thing is, once you clear reports, you only have 30 days of data to draw upon.
If that’s not a problem for you, then clear out the alert files and rebuild the reports using an executable in the sonicwall directory called mlfmfeimport.exe
Use the -help switch to get instructions on how to run it.