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@pixelgate.net> To: NANOG list <nanog@nanog.org> Subject: Re: Charter and Cox contacts Message-ID: <alpine.LNX.2.00.1905141115120.5030@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@pyranah.com 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). /mark Daniel Temple VP of Operations Pyranah Communications, LLC 828-743-2470 ext.205 Pyranah.com Like us on Facebook!