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Additional Email Settings Information

Last Updated: Mon, 01 Aug 2016 > Related Articles

37 rated this


Learn about third party SMTP servers, virtual domains, Port 25 restrictions, and view FAQs.


Cox requires all email messages sent from its network to go through Cox outbound email servers. Outbound email servers are known by the acronym SMTP. Any attempt to send email using a third party outbound email server results in an error message and an undelivered message.

Using Cox email servers is required to reduce the amount of unsolicited email, or spam, that is sent from the Cox network. Spam is not only a nuisance, but it can degrade email service by consuming network and server resources. Spam also increases the potential for computer virus attacks. Finally, excessive amounts of spam originating from our network can result in other Internet service providers (ISPs) refusing to receive any email, including legitimate messages, from our network.

You may be connecting to a third party email server for one of the following reasons.

  • Your email software, such as Outlook Express, is configured to use a third party outgoing email servers to send email, with or without your knowledge.
  • Your computer may be allowing other Internet users to connect to it. These outside users may be using your machine to relay their email. We recommend that you review your PC security.
  • Your computer may be infected with a virus attempting to spread itself through email. We recommend that you update your anti-virus software and scan your machine for viruses.

Vanity Domains

Although Cox does not currently host or support vanity domains, some customers acquire them through third parties and want to use them in their email messaging. Cox doesn't prevent using vanity domains, in either the From or Reply-To addresses, as part of your email header. However, if you use a vanity domain on your email, it must be a valid domain that can be resolved by Domain Name System (DNS) servers. Any email sent with invalid domains in the From or Reply-To address fields will not be delivered.


Does this mean that I have to use my @cox.net email address for everything I send?

No. You can use any valid email address, but the email sent from your Cox High Speed Internet connection must route through a Cox SMTP server.

What are the correct SMTP server settings to use with the Cox High Speed Internet service?

For more information on setting up your email, refer to Resources for Setting Up Cox.net Email.

Why do you require the use of Cox outbound email servers or SMTP?

It reduces the amount of spam and virus email originating from our customers. Most ISPs have adopted this practice to reduce spam. We must take this action to ensure that a few bulk email senders do not get the entire cox.net domain blacklisted from sending mail to other ISPs.

Does this hinder my ability to send email?

This doesn't impact the majority of customers, but some may be using third party mail servers. Any software configured to use an SMTP server other than smtp.cox.net to deliver email directly to a recipient's server doesn't work. You may receive an error message similar to the following in your mail client.

A time-out occurred while communicating with the server. Account: otheraccount.otherisp.com, Server: othersmtp.otherisp.com, Protocol: SMTP, Port 25, Secure(SSL): No, Error Number: 0x800CCC19.

Customers using third party email services must configure their email clients to use smtp.cox.net to send outbound email. Please note that operating an email or other server on a residential Cox High Speed Internet connection is a violation of our Acceptable Use Policy.

Does this affect web-based email services?

No. You can continue using Cox High Speed Internet WebMail, or other services such as Gmail or Yahoo mail, as you currently do.

Does this affect inbound email at all?

No. This doesn't affect the retrieval of inbound email from any service.

Does this mean that Cox reads my mail?

No. This measure only affects how traffic is routed and does not in any way relate to the substance of email messages. We respect your privacy and do not read any email messages, instant messages, online chats, or the content of other online communication that reside on or pass through our service. For more information, refer to our Privacy Policy.

I am getting spam even though I have never given out my address. Is Cox selling my information?

We do not sell customer email addresses. Sometimes spammers will try lists of common names or words in different combinations to locate active email addresses. For more information, go to our Privacy Policy. To learn more about how to reduce spam, refer to Protecting Yourself from Spam.

I am still receiving spam. How do I stop it?

This is just one step in efforts to reduce spam across the Internet. For more information, refer to Spam Resource Center.

I pay for my own domain name so I can send personal email through that server. Why are you blocking this legitimate use?

We understand that some customers have vanity domain names, and this action should not keep you from using your personal domain name. To ensure your ability to send email from your personal domain, your mail client must be set to a Cox outgoing mail server otherwise known as SMTP. This change in settings will be transparent to email recipients, and will not impact your ability to receive email. If you have a business requirement to bypass the Cox mail servers, please contact Cox Business Services for additional options.

What are Cox customers who send mail via Port 25 supposed to do?

Customers must configure their email clients to use smtp.cox.net to send outbound email. Operating an email or other server on a residential Cox High Speed Internet connection is a violation of our Acceptable Use Policy.

Does Cox offer SMTP authentication or POP before Send capabilities so I can continue to use my Cox account while on the road?

Cox does support SMTP authentication. Refer to Email Server Names for configuration information.

My settings are correct but I am using a return address other than @cox.net and I receive an error.

As part of our spam prevention procedures, we test the domain name in the From: address in each message to ensure it is valid. If the Domain Name Service doesn't show that the domain name has a valid mail server, those server connections are rejected. The customer may receive an error message similar to the following in an email client.

The message could not be sent because the server rejected the sender's email address. The sender's email address was ...

Customers should use their Cox.net email address or any other valid address in the From: field.

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