Comcast Moves to Block Port 25 for Residential Customers

Comcast has recently announced several changes to its residential Internet service.  The most notable change is the block of TCP port 25.  Port 25 is the default SMTP port used to send email on the Internet.  Most email clients by default use port 25 to send email.  The net effect of this block is that all SMTP clients trying to deliver email on port 25 will fail.

The good news is that SocketLabs can help. Our SMTP Relay service supports alternate SMTP ports that you can configure in your applications to bypass this Comcast restriction. If you are not a SocketLabs customer, you can sign up for free here.

So how can SocketLabs customers work around this new port 25 block?  Simply change your applications to relay through SocketLabs On-Demand over the alternate ports 2525 or 587.

These new changes at Comcast are only for residential customers and do not affect Comcast Business Class customers.

For full information on the changes at Comcast read the entire Comcast blog.

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