From time to time (and especially recently), we will get a call or an email that someone isn’t able to receive email from a particular person because their email is being blocked.      The reasons for this are usually pretty simple and can be narrowed down to one of the following:

  • the mail service the person is using is also used by spammers so they need to change to a more reputable mail service.   this typically seems to happen frequently with Hotmail and Yahoo addresses.
  • the service provider of the person is currently being used to send spam and may be blocked until they rectify the problem.     Many service providers have been through this and are quick to resolve the issue and all is typically back to normal within a few hours.   In most cases, the bounced email will have information as to what is causing the bounce and even a link to more information.
  • the mail server of the person is connected to a cable or DSL connection from a company such as Shaw or Telus and they are sending out email directly from the server.

Unfortunately, blocking spam has become a never-ending war between spam detection and detection avoidance.    Service providers are constantly looking for new methods to reduce spam.

One of the methods used to do this is to use PTR record filtering.     This can reduce spam considerably and typically filters out email that originates from cable users on the Shaw network.

The truth is, there is really no reason why legitimate email should be sent directly from any server connected to the Shaw cable network.     Pretty much all email being sent from consumer broadband connections is SPAM of some type.   Shaw users are typically encouraged to use Shaw’s SMTP servers.

The problem is that an expansion of this technique is to simply use RBL filters to prevent any connection from servers on what is considered, correctly or not, a dynamic address range.     Some Shaw business connections have static IP addresses within these ranges and can be blocked as well.

The simple solution to this is to either use your service provider’s SMTP server as your smarthost (or relay host) or subscribe to a service that will permit you to relay your email safely and effectively.

So, if you are finding that your email is being blocked, check the error message for a link to what may give you the answer as to why it’s being blocked.    If may be a simple matter of properly configuring your mail server or changing to a reputable mail provider.

Jamie Penner has nearly 30 years of experience in developing, operating, troubleshooting, and implementing email servers and spam/virus detection.