To me it doesn't sound like the smtp or delivery logs will help on your server. If I understand, a message sent from your wordpress site, is sent to a hotmail address. Probably authenticating through your smartermail email account.... is that correct?
If that is the case, you will need to look at the header of the hotmail account, and see what is failing. If it went to the junk box, then it sent.... hotmail got the message, it just applied their spam filter to it.
Along with Bruces suggestion, get the email header from the hotmail account.
Remember kids, every time a spam message gets blocked, a nerd gets their glasses. spamhurts/July 15