Hotmail does not use live DNS for the sender ID, but they have a DNS cache that they update twice a day. TempError simply means that the SPF record of your domain is not in the cache. Simply send an e-mail message with your domain to email@example.com to cache your record. They will add it, but be patient because it is a manual process and the cache is only updated twice a day. This is due to the PTR mechanisms, which only match when the required data is in Hotmail's cache. While PTR has an increased risk compared to other mechanisms due to the quality of reverse DNS information, the PTR is particularly risky with Hotmail.