Text shows something different than what is there.

[Steve Campbell]

Sorry if this has been discussed before. I may have not realized what 
was being discussed until I saw it in front of me.

We are getting tons of email with different sexual content. When viewing 
the source of the email through Thunderbird, a few of the lines show up 
like the following:

IF YOU WANT TO F wol UC sty K SOMEBODY,
F oy U zb CK YOURSELF & SAVE YOUR MONEY!

The email when viewed normally through Thunderbird (and probably most 
other clients) is different. If you remove all of the lower case letters 
and the spaces around them, you'll see what the viewed text is displaying.

Can anyone explain what is going on there and a pretty good way to block 
this. The F-word is pretty blatant in these.

Thanks,

Steve Campbell