More Zen Internet woes...

Two months ago, I reported systemic issues with Zen Internet's IP block management, eventually resolved after a number of days by the creation of missing reverse DNS (rDNS) records.

I've only just discovered that (at least) this subnet of "static" IP addresses, possibly more, has been listed - presumably by Zen Internet - on a real-time block list (RBL) of IP addresses used by Trend Micro customers to prevent spam being received from IP addresses dynamically allocated to dial-up users, i.e. a group of people that has become vanishingly small in recent years, and will disappear completely if the 2025 changeover to 100% IP telephony actually happens.

You just couldn't write this stuff. Zen Internet has been informed, but new customers thinking of hosting MTAs on their "static" IP address might just want to check that it isn't listed on the Trend Micro checker here.

And as the removal of my IP address from the RBL could take up to 48 hours to propagate around the Internet, I can't contact the affected recipient by e-mail until that happens.

Sigh.

Edited by deleted (Tue 12-Jul-22 20:48:12)

My address is also blacklisted - 88.98.87.xxx

In reply to a post by ukwiz:

My address is also blacklisted - 88.98.87.xxx

I should have included mine... 51.155.204.xxx - a completely different IP block, but also wrongly listed as being used by whatever dial-up customers Zen still has...

Double sigh...

82.69.100.xxx is also blacklisted. Zen insist it is because the address doesn't have a reverse dns. Why should it when it is not running any servers

I have had this IP a long time and it does have a rDNS but at least its not every Zen address!

IP: 82.68.x.x
Reputation: Unlisted in the spam sender list
Listed in: None

Mine too.

88.97.10x.xx

Probably includes everybody!

In reply to a post by ukwiz:

82.69.100.xxx is also blacklisted. Zen insist it is because the address doesn't have a reverse dns. Why should it when it is not running any servers

https://mxtoolbox.com/problem/smtp/smtp-reverse-dns-...

What it needs is for Zen to register their static ip addresses.Of course, with Zen that is unlikely to happen.

That’s not really how it works…

There are many MANY RBLs out there. Each of them generate their list based on different things. A lot of them start by looking at the rDNS for an IP. If it appears autogenerated (88-98-240-10.dsl.zen.co.uk for example) then the lists add it to a blacklist. Not because it’s dial-up, but because it’s likely a residential service so unlikely to be running an MTA.

If you want to run an MTA, then Zen provide the tools for you to set an rDNS record that looks more legitimate so can avoid RBLs.

There is nowhere to ‘register’ an IP address as being for a certain use, and there are so many RBLs that it’s not feasible for an ISP to routinely try and ensure that it’s IPs are not listed on them all, especially when for the vast majority of customers it makes little difference. The bulk of customers are not running MTAs.

Any sysadmin worth there salt knows about this, so will ensure this is all in line before moving production service onto a new mail platform.

In addition to this, companies that are still running their own email infrastructure are likely to use a smart host which may also be providing their inbound filtering - Mimecast, Proofpoint etc. and so the reputation of the originating IP isn't important. If you're sending mail directly from a server you run yourself and it's a production system (which it appears to be as this problem is inconveniencing you) then what was your contingency plan for a broadband outage?