Please note: Telnet is disabled on newer versions of Microsoft Windows. Once on the command line, type: (Note! Be sure that you replace with your actual domain name) telnet 25 Mac users can use the “ Terminal” application. For windows users, you can access this via start > run > cmd. To test if port 25 is blocked, open your command line on your local computer. For the advanced user, we’ve included directions below to test port 25 blocking via Telnet and the command-line interface. This can be the case even if sending was working recently as some ISP’s roll these changes through without warning.įor the average user, the easiest way to find out if port 25 is being blocked is to contact your ISP and ask them. If you cannot send mail, the problem is likely a restriction by your ISP (Internet Service Provider) as many block the normal sendmail port 25, due to their own security concerns. Looking for a host that provides flexible virtual private servers? Look no further than InMotion’s VPS Hosting solutions! Managed and Self-managed Cloud servers provide a wide variety of scalable secure option for your website or application needs. If you are unsure how to make the above changes, we recommend reviewing our Email: Getting Started Guide. Secure Authentication or SPA needs to be turned off