You you be more specific on how you have your e-mail settings? And, what type of e-mail are you using (IMAP or POP) and are you accessing your e-mail through the Safari app or the Mail app? Oh, and what do you mean that the emails disappear - they are gone when you go back to the mail program, they are disappearing before your eyes, etc.?
A few more details may help us better understand your issue so we can help. Thanks.
Marilyn