Tuesday, April 24, 2018

Does Anyone Have a List of Valid Email Domains?

The response from my ISP's support is:
(1) The message was sent from a mail server which is listed as a verified spam source on major real time blacklists (RBLs)
(2) The message was sent from a mail server which doesn't have a valid forward confirmed reverse DNS (FCrDNS) record
While all properly configured mail servers have reverse DNS records which check out backward and forward (the mail server's IP points to a valid host name, and that host name is likewise pointed to the same IP) and there is no way to disable that check if you wish to make sure that all other mail is delivered to your Inbox it is possible to request that one or all of your domains be added to a special "skip RBL check" list.
If we do this no incoming mail will be bounced due to it coming from a verified spam source/blacklisted mail server. While this would help guarantee that all wanted incoming mail reaches you please note that this change may (and likely will) cause an increase in unwanted spam to your domain's inboxes. 
It appears that I need to whitelist every conceivably valid mail server.  Can you all provide a list of your email domains?  (One on each line, in comments.)  It is hard to imagine so many misconfigured mail servers.


  1. You don't need to white list. If the mail was rejected, it's because it's coming from a shady looking server that's on a real-time black hole list, or it's otherwise not properly configured. The solution is for the sender to fix their mail server.

  2. There is no such list and there cannot be such a list.

  3. People who buy the domain name for their own website often set up an e-mail server which services that website.

    You, for example, own claytoncramer.com. If you set up an email server, you could be "theman@claytoncramer.com", potentially making your website a valid email domain.

    Spammers take advantage of this by licensing nonsense for short term use and using it to send spam (or denial of service attacks) versus to mailboxes for a list of pregenerated, random, or computer predicted email addresses.

    So while you could likely capture 95% + of the email addresses out there by adding the big domains like @gmail.com, @cox.net, @hotmail.com, comcast.net, @yahoo.com, etc., in theory the number of valid domains is unlimited.

    I use gmail, so I am sure you got that covered.

  4. I've never heard of people having to whitelist their server domains before (I'd change ISPs, but maybe it's not possible to get a good one where you are)- but here are mine:

    1/ @gmail.com
    2/ @roadrunner.com
    3/ @protonmail.com

    Hope that helps. Let us know how it's going, please!

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  6. Sebastian: How do I know an email is being rejected if it never arrives?

  7. Sounds like you have the wrong ISP.

  8. Sebastian is correct. One of our relatives was having the same problem sending email to us (via suddenlink.net, which is a valid email domain) because our ISP (earthlink.net) identified one of their servers as a spam source or improperly configured. Emails from the relative that did not go through that "bad" server came through just fine. In suddenlink's case, they have multiple servers, each with it's own IP address. The relative had to hassle suddenlink to get it fixed. Took a while, but eventually suddenlink did fix it. Meantime, it was common for the relative to have to re-send emails.