Stopping messages with the "Re: ??" Subject

[Chris Hammond]

The MailScanner server that I maintain get's hit with 3k-5k of of these messages a day.  They are all spam and the subject is in the form of the Re: with a space and two letters.  The first letter can be any from a to z, while the second letter is either a e i o u or y.  I created the following rule as a Postfix header check as I want to flat out reject these messages.

/^Subject: (Re: [a-z][aeiouy])/ REJECT Spam 30-25.    -    First attempt
/^Subject: Re: [a-z][aeiouy]/ REJECT Spam 30-25.      -    Second attempt
/^Subject: (Re:) [a-z][aeiouy]/ REJECT Spam 30-25.    -    Third attemp

The problem that I am having is that it doesn't stop after the two letters.  If a word after Re: that matches one of the two letter combinations comes up, it fires on that also.  What am I doing wrong with the rule.  I only want it to fire on the Re: and the two letters.  Nothing more.

Thanks
Chris