What MTA (local mail server? Gmail?) is your osTicket using to send mail?Microsoft (Outlook/hotmail/Exchangeonline) has a blacklist processor that acts on incoming email prior to the filter that puts messages in the spam folder.It is likely your messages are being killed by that step, and there is nothing on the Hotmail/outlook side that shows that. You would have to check the logs on whatever server osTicket is connecting to to send the messages. If Microsoft is blacklisting you, your MTA logs should have a Status 5.5.0 message saying so.