Ever since initial use of windows Live mail I have had problems

There are some messages (probably malicious) in the Junk email folder which I cannot delete and Unknown error message is displayed Recently I tried to delete one and a mwindow popped up saying deleting message but nothing happened. After a delay I tried cancelling it and again nothing happened. It locked the display and I had to restart to recover.

However the major problem is that when I open Windows live mail it attempts to send 2 messages and fails. one of these messages I recently tried to send with a large attachment and it takes over 30 minutes retrying to sent it.  I receive a failure message.

This message could not be sent because its size exceeded the server's limit. You can use the option, located in Tools | Accounts | Properties | Advanced, to break messages into smaller parts.

Subject 'Vivs 50th'
Server Error: 552
Server Response: 552 5.3.4 Error: message file too big
Server: 'smtp.mypostoffice.co.uk'
Windows Live Mail Error ID: 0x800CCC6D
Protocol: SMTP
Port: 25
Secure(SSL): No

Neither of these messages appear in the folders so I cannot see how to delete tham

Can you help