Many home DSL and cable internet service providers block what's known as port 25. This is the outgoing (SMTP) email port. They do this to help prevent spammers from ordering an inexpensive internet service then using a basic server, send out junk mail. Also, this helps prevent spyware/adware/malware from spreading through the use of email since they typically have their own email server software instead of using your email account.
HOW TO FIX THE ISSUE
Some internet service providers will unblock port 25 upon your request. Some like DSLExtreme have a dedicated page on their website that allows you to request the ublocking of this port. Some providers will tell you that you need to use their outgoing email server because they cannot unblock the port for you. If you need to use their outgoing email server, you will need to edit your email account on your computer and change only the outgoing (SMTP) server to the server that your provider gives you. You may also need to use your email address/username and password for your email account that is setup with your current provider. Make sure you add the email address that you are setting up to the "Reply to" line in your email program. Your internet service provider should be able to provide you with the necessary information.
You may encounter some problems setting up your email this way. For example, your email address may be you@yourcompany.com but your email be actually coming from you@yourprovider.com. The recipient will not see this email address if you add your company email address in the "Reply to" field in your email program. The issue is that some spam blocking software on the recipients side may see the actual email address instead of your company email address. So you may have to give everyone your personal email address so they can setup their software properly. This may not look very professional. Unfortunately, your choices are to complain to your provider and possibly take your business elseware if they will not unblock port 25 or upgrade your account to a business class service. If your internet service provider offers a true business class DSL/cable service, then port 25 should not be blocked.
