A Vista PC which was sending SMTP mail fine on Port 25, suddenly stopped. I have fixed the problem by sending on Port 587 - but what I want to know is why? I know this much:
1. It's not the AV/Firewall (PCCillin2007) as turning the software off makes no difference.
2. It's not the WIndows Firewall -it is not turned on.
3. It's not the firewall on the router -XP PCs on the same network can send on Port 25 with no problem. This also shows that it is not the ISP's mail server.
4. I have tried Telneting into the SMTP server. It hangs until you hit Control C - then you get in to the server and communicate with it.
Can anyone tell me what is going on?
Work with freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely, and get projects done right.