ES000001: sending from an Xfinity residential IP
Xfinity blocked mail sent from a dynamic or residential Xfinity IP address by a server other than smtp.comcast.net. Send through Xfinity, or use a business connection.
- Comcast
- Provider
- Sources checked
- Author
At a glance
- Code
- ES000001
- Provider
- Comcast (Xfinity)
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
What it means
Xfinity does not let its customers send email through mail servers other than smtp.comcast.net. ES000001 means the connection came from a dynamic or residential IP address on Xfinity's own network, from some other server, so Xfinity blocked it from sending to the Xfinity network. Examples are a mail server run on a home connection, a device that sends alerts directly, or a mail program set to deliver mail itself. Mail sent through smtp.comcast.net, or through the Xfinity webmail app, goes the way Xfinity expects. For running your own mail server, Xfinity suggests a Comcast Business account.
Common causes
- A mail server running on a home Xfinity connection is delivering mail directly.
- A device or application on the home network sends mail straight to recipients instead of through smtp.comcast.net.
- A mail program is set up with the wrong outgoing server.
How to fix it
- 01Send through the Xfinity webmail app, or set your mail program to use smtp.comcast.net as its outgoing server.
- 02Point devices and applications that send mail at an authenticated outgoing server so they do not deliver directly.
- 03If you need to run your own mail server, move it to a connection meant for one, such as a Comcast Business account, or to a hosted provider.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
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