Charter and Cox contacts

daniel at daniel at
Wed May 15 13:26:06 UTC 2019

First off, I apologize for the list. I didn't realize my replies included the entire original email... 
Mark, we do not run a mail server. The issue is a lot of our customers have their 2nd homes here, 
so when they come up they are using their email provided by their 1st home ISP. 
A number of our customers use Cox, Charter, and Spectrum and can receive email just fine but cannot send. 
Report from a mac book pro email client showed Cox to be blocking the IP that we NAT most customers through.

Message: 7
Date: Tue, 14 May 2019 11:22:41 -0700 (PDT)
From: Mark Milhollan <mlm at>
To: NANOG list <nanog at>
Subject: Re: Charter and Cox contacts
Message-ID: <alpine.LNX.2.00.1905141115120.5030 at arcghar.ybpny>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed

On Mon, 13 May 2019, Stephen Satchell wrote:
>On 5/13/19 12:11 PM, daniel at wrote:

>>Does anyone have contacts at Charter (Spectrum) and Cox? For some reason,
>>our IP has been blocked by them and our customers are unable to send email
>>via their charter/cox accounts. Thanks
>Would you be talking about port 25/tcp outbound?  Lots of ISPs will
>block port 25 as a rule;

If this is the case, that your customers cannot use your mail servers to 
relay mail then provide port 587/TCP (SUBMISSION) or even 465/TCP 
(SMTPS, deprecated).

If you mean that your mail servers can't send mail to Charter and Cox 
addresses, then indeed you need to find out what happened, fix it then 
request removal from their (and other) blacklists for which contacts 
there would be helpful (I am not one).


Daniel Temple
VP of Operations
Pyranah Communications, LLC
828-743-2470 ext.205
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