If your legitimate email messages have been caught or blocked by an Internet service provider, you're not alone. Many small businesses and individuals have had perfectly legitimate messages returned or dumped by overzealous ISPs trying to stem the ever-increasing tide of spam.  There are steps you can take to avoid your emails meeting this fate, but first you need a basic understanding on how your ISP operates in order to find the right method to authenticate your messages.

Spam not only infuriates email users, but it also clogs up servers and costs ISPs time and money - not to mention customer goodwill. Since the start-up of electronic communications, spam has been a problem. As volume has increased, so has spam - which has spawned many more problematic varieties including missives laced with spyware or malware. It used to be that being a customer of a well-established Internet service provider like AT&T was all the proof you needed to be considered an authentic customer. Spam-blocking tactics were directed toward outsiders - unknown or dubious ISPs and non-customers. The tide turned in 2008 when certain large ISPs started blocking email from any account with an Internet provider that had been identified as a source of spam. Ironically, this measure blocked many of the large ISPs' own legitimate customers. It was at this juncture that AT&T elected to get out of the email business. AT&T customers are directed to Yahoo! Mail to register email addresses in order to use Yahoo! Mail for their messaging service.

It's smart for businesses to be pro-active and ensure that email messages are not being caught up, delayed or dumped as part of aggressive restrictions imposed by some of the more powerful Internet gatekeepers. Here are some measures you might consider implementing:

1. Your Internet service provider offers something called a Simple Mail Transfer Protocol, which is designed to take your outgoing email and get it started on its path to the intended recipient(s). Find out what authentication procedures your ISP uses. Most require that each outgoing message is accompanied by a username and password. If you receive a message stating Authentication Required or Relaying Denied, your ISP is not recognizing you as a legitimate customer. You need to reset your SMTP setting - SMTP: (ISP Name).com - to the correct name of your Internet provider and change the SMTP port to 587 to allow authentication over the Secure Sockets Layer (more commonly known as SSL).
2. Make sure that the SMTP your Internet provider uses has not ended up on a Domain Name System block list. DNS servers communicate with each other using private network protocols. The DNS hierarchy means that there are 13 top-tier servers that contain the complete database of domain names and Internet Provider addresses. There are many DNS block lists associated with the server system (spamcop.net, cbl.abuseat.org or spamhaus.org, to name a few) and most are run and maintained properly. If you are having trouble, check to see if the SMTP you use has ended up on a DNS list. You are more likely to run into this type of problem if your email is associated with your own domain name and a private server.
3. If you get a MAILER-DAMEON message explaining that your message was rejected because it was on a block list of a specific DNS, you can contact them through the link provided in the error message to find out how to remove your STMP from the list. The problem can be resolved, but it might take several days.