Lost password reset email

I’m having trouble with a user of my blog site not receiving password reset messages. They are using GoDaddy as an email host, all their spam filters are disabled so everything from anyone goes through and gets picked up by their email client. The email address for this user is correct by virtue of the fact that when they post a message to the blog, they receive reply comments to that email address with no difficulty or loss of messages. So, where are the password reset messages going, and how can I determine if they are being bounced and returned to sender? I’m running this WP on a Ubuntu system with postfix as the MTA and am not all that familiar with the inner workings of postfix, but I’m thinking there’s got to be a log somewhere in there I can look at to find returned undeliverable email messages, yes?

Thanks in aadvance for any and all suggestions as to how to find where these password reset messages are going.