Outlook & Hotmail randomly junking company emails

Hi

we are having some major problems with our customers using Outlook or Hotmail. Our mails are randomly being sent to junk. I can send the same test mail twice, one will go to junk the other will go to the inbox.

Even if the user whitelists our email / domain, it STILL goes into junk.

We are on no blacklists, we do not send spam or any unsolicited mail. We are with a reputable host who does not tolerate any spam. Our newsletter requires double-confirmation, and adheres to all industry standard marketing mail best practices. In the mail headers, all checks (SPF etc) are passed. There is nothing in any of the headers that suggests there is a problem with the mails. Plus the fact that even whitelisted the mails do not hit the inbox.

I have raised a support ticket (SR1501859960) about this. You are preventing us from communicating with our customers. We would appreciate a response to this issue thanks.