 3 problems
There are 3 problems. You don't have a postmaster account set up, so you're not getting bounce notifications - you can add postmaster as an alias to another account, if you like - this will help debug further mail problems.
The 2nd problem is that ldap lookups are timing out - how high is the load on this server? We've seen this when the host is overloaded, at times.
The main problem, however, seems to be DNS - it appears that your host can't find a valid MX record for hotmail.com, and is refusing the message (a retryable error - 4xx error codes are non-fatal) |