When you check your crontab file with crontab -e do you mean that the file is totally empty?
Are you sure there is no mailto line at the top of the file?
If you do have any crontab events set up do you have :-
at the end of any crontab lines to ignore error and normal cron output?
Do you have any programs that would backup a data file?
If you answer yes, yes, no, no then you may want to contact support. It is possible that someone has set up a mailto line somewhere in error using your email address instead of their own.
If you answer yes, yes, no, yes then check that programs configuration to see if it includes an option to turn off notifications.
Opinions are my own views and not the views of DreamHost.
Any advice offered by me should be acted upon at your own risk.