Hotmail blocking Gov emails at firewall level

Hi Microsoft,

We have determined that an auto generated email from https://nppes.cms.hhs.gov/IAWeb/login.do after sign up is being blocked to send to hotmail accounts. We have tested and it works fine with gmail, yahoo, etc, but hotmail appears to be blocking it. It does not even arrive in the junk folder so it seems to be at the firewall level.

I can provide the email that is used to send these, but do not want to post it for the public to see.

We also discovered that adding the email as a safe sender will allow the email through, however they cannot re-sign up with the same email to regenerate the email.

Please reply asap as to how we can proceed to unblock this issue where it is being blocked.

Thanks,

steve