This may occur due to several reasons. Firstly it may be due to the bad telephone band width. Secondly it happened because of your local mail server functionality or due to heavy load. Thirdly depends up on the internet server capability. Need to be isolated, to find the reason.

How i can secure lose of mail or mail bounces? ( 10th Jan 2007, Mrs.Rani, Coimbatore)

Always check whether the quantum provided for you have enough space to receive mails. Kindly try to free your inbox after reading. If it is required for long, maintain a backup on your local machine. Try to check up with the person whom you have purchased the email space, whether the server has backup facility. If so, there will be 100% no lose of email. Its advisable to go for secured hosting always. 

How do i can restrict the email virus 100%, Recommend a powerfull virus scanner? (2nd Jan 2007, Mr. Anil, Delhi)

Virus, Worms are created due to many active functionality’s. There are many professional version of Viruswall’s available for desktop and server level security. Keep updating your virus scanner. Even though you cannot make your machine 100% virus free, because script over writing viruses are created due to unauthorized access to memory. Many newly created viruses cannot be identified immediately.