My e-mail accounts are using POP3 setting, and i have "do not delete message from server" checked and "delete message from server when delete from the computer".

There is a tag showing "A copy of message is on the sever" at first after downloaded, but after probably 1 month, the tag is gone, n outlook will download the same message again. 

Is there anyone have idea how to solve the problem?

This is quite annoying. 

Thanks in advance