Why does MS Outlook not allow global blocks

Hi, 

Today i was blocking some spammers from my email and it occured to me that this could be so simple if MS Outlook would allow us to block global email address.   For example why can't i block 

*@*.ru.ac.th

Which just sent me a tone of junk, the senders get around this by just changing a small part of the email address but the main part the end is always the same, so why can't i block it? When i try, outlook tells me it is invalid.

Thanks