I’ve got a weird problem at work with Outlook. All of a sudden, some PCs stopped sending mail via the ISP’s STMP server. I have 2 Vista Ultimate PCs with Outlook 2003 and they are working fine (Very odd, but true), a couple XP Pro PCs with Outlook XP and some others with Windows 2000 with Outlook 2000. I keep getting the following error: “Task mail – Sending reported error (0x800CCC0F) : ‘The connection to the server was interrupted. If the problem continues, contact your server administrator or Internet service provider (ISP).’” I have tried everything I could think of to get it back working. The ISP is not at fault cause as I mentioned earlier the Vista PCs working fine. I have tested the STMP port via telnet and it connects perfectly. I have increased the time-out to 10 minutes and that does nothing. I have run the Office Detect and Repair, also tried uninstalling and reinstalling Office. I even tried using another logon account with a clean account, still the same error. I noticed that the “Test account setting” works fine and even sends the test e-mail. I tried sending an e-mail in Plain Text and it manages to send, but no attachments. The strange thing is that no changes were done and yet some PCs manage to send e-mail and yet most don't. I have tried sending with Outlook Express and it does work. Any help?