I suggest you first check the SMTP related. Since you can log on Outlook Web App (OWA) without any problems, it means the mail service works fine. X-CTCH-RefID: str=0001.0A0B0205.505353B8.01BE,ss=1,re=0.000,fgs=0 First of all, I want to set up an expectation that the mail client is Thunderbird, which is not a Microsoft product. Received: from () by with Microsoft SMTPSVC(.4900) Search: Mozilla Thunderbird Problems Sending Emails. X-Message-Info: q7bX5s87Og//UscsqJoXfqWRrjzd8fmc6+iJXdUrjlCguCbG/cy+3AzjpVLYdZP7/emaDEnxc3V2KRnvsABVoTFJuAFcD5v+VEAK91CTsdIGeBY8AX0q8bPZJ7oemwmK34VLwdlshLYNbrvMoGR2cg= X-Message-Delivery: Vj0xLjE7dXM9MDtsPTA7YT0wO0Q9MjtHRD0yO1NDTD00 After closing Mozilla Thunderbird the uninstallation of Kaspersky Internet Security 2009 went through without problems. Mail was not marked as junk anymore and the manual Junk controls (mark mail as Junk or Run Junk Mail Controls On Folder) did not have any effect as well. X-store-info:4r51+eLowCe79NzwdU2kRwMf1FfZT+JrstzdFG76XYG4p+n5Kt5O1NDgyG6DnTEYpkceVS/buEc7897HoAy+vRXUP3AKhDp74CpjOfLkPd8yylLK0VPldHYbwF0iZoD+s4UGAqqvWyg=Īuthentication-Results: sender-id=fail (sender IP is 151.1.108.65) dkim=none header.d= x-hmca=fail The Junk Mail filter in Thunderbird stopped working suddenly. This is the message source sent from thunderbird (I only replaced the email addresses whit it reports 'sender-id: fail' :

Mozilla thunderbird hotmail not working