radacct mysql query for badguy

[Andys Pool Shop]

Greetings everyone, 

I have a bad guy that keeps sending harassment emails from a well-known 
web-mail acct.
I know he has httpd an email on 2005-12-15 08:57:32
I have tried to query mySQL radacct but, I left my level of expertise.
Please don't be brutal, I know..Go to the the mySQL list.
But since radius logs are for security too, I thought this list would help 
me.
Can someone tell me the best SELECT statements to use, so I can narrow my 
search?
My problems come when I try to SELECT UserName FROM radacct WHERE 
AcctStartTime with the date/time format syntax
We are a very small and only have 46 dial-up ports so any returned results 
would be most satisfying.