Time issue with Entourage

My boss uses Entourage for her mail. Lately however when she logs into her computer and opens the program she notices that several of her new e-mails have the same date and time. It could be anywhere from 5 to 20 that are like this. It use to happen only now and then, but is happening more and more now. Does anyone know what the issue could be. It's obvious all these e-mails were not sent at the same time, I am not sure if it's a setting on the program or a problem with the program and our network connection or what. Any help? Thank you.