Shaw blocking port 25 outbound

Well it has been happening all summer but Shaw has been slowing blocking port 25 outbound on their connections. They are probably one of the last ISPs in North America to do so.

Does this affect you? Probably not! If you do use email accounts other than Shaw’s you probably are or will be affected. Here is what is happening, Shaw blocks port 25 outbound which is the port that email servers use to send and receive email. By blocking port 25 outbound your mail client can’t communicate on that port to your mail server. and therefore cannot send email. Telus has been doing this for sometime now and I was first made aware of Shaw’s changes in May of 2007. About a month later my connection started doing the same thing.

Their rational behind this is that it reduces outbound spam from their network, where in actuality one of the side affects is that it can make your non Shaw email look more like spam because of one of the methods of working around the block. 

This restriction can affect you if you have your own domain email, or if you use pop3 services for Gmail, Hotmail, AOL etc.

How can you work around it? Well if you have your own domain and use that email server, see if your hosting provider can set up your sendmail program (or mail server) on an alternate port (like 2525). If this is done go into your mail client’s advanced settings for the account and change the smtp port to the port that was provided. You should now be able to send to your own server.

If you don’t have the option to change the ports you will have to send email out via the Shaw (or Telus mail servers if your are with them) . Go into the account settings for your mail client and set the outgoing servers as your ISPs. For example with Shaw cable in Calgary it is  If you are using a mail server other than your own domain you are essential done (although it is possible that you email will be marked as spam because the sending domain will not match the email domain). If you are using your own domain there is one other step you have to do. In order for your email not to be tagged as possible spam, make sure that you create an SPF record for your domain including your ISPs mail servers as authorized servers to send mail for your domain.

There are several web based wizards available that will walk you through the process of creating the SPF record (Microsoft has a good one). Create your SPF record and either add it (or have it added) to your DNS records as a txt record. This tells other mail servers that use SPF that your ISPs mail server is authorized to send on behalf of your domain and therefore it is less likely to be tagged as a spam email.

I have checked and this affects both personal Shaw accounts and commercial accounts. However my server running on a static IP address works fine.

Just another way that spammers have ruined our Internet experience!

Technorati Tags: , , , , , , , , ,

Leave a Reply

Your email address will not be published. Required fields are marked *