wrong date

Hi 

one of the application triggers emails. When the emails are received in the mailbox, date is showing wrong for example application triggers email today, and email is received in the users mailbox. The date of receiving shows 4 to 5 days back date(for example  on May 11 application triggers email). On application side it shows that email has trigged today but in the mailbox its shows may 06 date. experts guide me.