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Comcast IP Address Persistently Blacklisted!

Posted by
Frequent Visitor

Message 1 of 4
734 Views

My IP address is being blocked by the Barracuda security appliance employed by my financial services consultant. That appliance uses the Spamhaus ZEN blacklist (see att.), which includes 67.168.170.26 , the dynamic address assigned by Comcast to my home router.

 

I rebooted the router in an attempt to obtain a different address and that worked very briefly but then the address apparently reverted and is once again being blocked. Is this some kind of 'sticky' IP address? As in:

"A sticky dynamic IP address is an informal term used by cable and DSL Internet access subscribers to describe a dynamically assigned IP address which seldom changes. The addresses are usually assigned with DHCP. Since the modems are usually powered on for extended periods of time, the address leases are usually set to long periods and simply renewed. If a modem is turned off and powered up again before the next expiration of the address lease, it will most likely receive the same IP address."

 

I need an address that is not included on the Spamhaus (global) blacklist. How do I make this happen? This is an urgent financial issue for me.

MX Block List.png
3 REPLIES
Posted by
Connection Expert

Message 2 of 4
727 Views

Are you using a router that has a MAC address cloning feature ?




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Posted by
Frequent Visitor

Message 3 of 4
661 Views

My thanks to EG for the suggestion around MAC address cloning: I was not aware that my Netgear Genie could/would do such a thing but in fact it has a ‘use PC MAC address’ option and that worked just fine, at least in the sense that it fooled Comcast into leasing me a new IP address. Sadly, that address experienced the same lack of love as the original one (i.e., Barracuda appliance still bounced emails from my Outlook client) so I went looking for a different explanation.

 

It turns out that both IP addresses were listed on a PBL (policy block list), not a classic blacklist. The following (https://www.spamhaus.org/pbl/) describes the difference:

”The Spamhaus PBL is a DNSBL database of end-user IP address ranges which should not be delivering unauthenticated SMTP email to any Internet mail server except those provided for specifically by an ISP for that customer's use. The PBL helps networks enforce their Acceptable Use Policy for dynamic and non-MTA customer IP ranges.”

 

For years now I’ve been pushing (i.e., SMTP) email out though a Gmail server without problems (notably including to the recipient in question); this even though my ISP is Comcast. Spamhaus and its adherents apparently view such email as ‘unauthenticated’ (since it comes from a ‘free’ relay) and they reject it without examination. Once I reconfigured my email client to use a Comcast relay the problem went away.

 

So my theory at this point is that my financial advisor’s site recently made a change to implement a ‘reject all’ policy for emails from relays on the PBL. I have no easy way to confirm this, but my emails are flowing again so I guess I can live with the uncertainty.

 

Hope these findings are helpful to others. Case closed.

Posted by
Connection Expert

Message 4 of 4
648 Views

Glad that you got it straightened out ! Smiley Happy




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