[Koha] Unable to send emails for Late orders

Dear All , i am using my send mail with my Gmail configured for sending mails from koha.the mail sending is working fine for check in checkouts .But for the late order claims its showing mail sent but neither i get an error message in Mail.log or i am able to see the mail in my sent mail.i am aslo unable to see any log for sent mail.kindly help me solve these issues . thanks and regards, vimal