It depends… no more

Ask Laura: Should we allow tagged addresses?

• laura
• Best practices

Do system administrators have too much power?

• meri
• Industry

Yesterday, Laura brought a thread from last week to my attention, and the old-school ISP admin and mail geek in me felt the need to jump up and say something in response to Paul’s comment. My text here is all my own, and is based upon personal experience as well as those of my friends. That said, I’m not speaking on their behalf, either. 🙂
I found Paul’s use of the word ‘SysAdmin’ to be a mighty wide (and — in my experience — probably incorrect) brush to be painting with, particularly when referring to operations at ISPs with any significant number of mailboxes. My fundamental opposition to use of the term comes down to this: It’s no longer 1998.
The sort of rogue (or perhaps ‘maverick’) behavior to which you refer absolutely used to be a thing, back when a clean 56k dial-up connection was the stuff of dreams and any ISP that had gone through the trouble to figure out how to get past the 64k user limit in the UNIX password file was considered both large and technically competent. Outside of a few edge cases, I don’t know many system administrators these days who are able to (whether by policy or by access controls) — much less want to — make such unilateral deliverability decisions.
While specialization may be for insects, it’s also inevitable whenever a system grows past a certain point. When I started in the field, there were entire ISPs that were one-man shows (at least on the technical side). This simply doesn’t scale. Eventually, you start breaking things up into departments, then into services, then teams assigned to services, then parts of services assigned to teams, and back up the other side of the mountain, until you end up with a whole department whose job it is to run one component of one service.
For instance, let’s take inbound (just inbound) email. It’s not uncommon for a large ISP to have several technical teams responsible for the processing of mail being sent to their users:

AHBL Wildcards the Internet

• josh
• Industry , Technical

AHBL (Abusive Host Blocking List) is a DNSBL (Domain Name Service Blacklist) that has been available since 2003 and is used by administrators to crowd-source spam sources, open proxies, and open relays.  By collecting the data into a single list, an email system can check this blacklist to determine if a message should be accepted or rejected. AHBL is managed by The Summit Open Source Development Group and they have decided after 11 years they no longer wish to maintain the blacklist.
A DNSBL works like this, a mail server checks the sender’s IP address of every inbound email against a blacklist and the blacklist responses with either, yes that IP address is on the blacklist or no I did not find that IP address on the list.  If an IP address is found on the list, the email administrator, based on the policies setup on their server, can take a number of actions such as rejecting the message, quarantining the message, or increasing the spam score of the email.
The administrators of AHBL have chosen to list the world as their shutdown strategy. The DNSBL now answers ‘yes’ to every query. The theory behind this strategy is that users of the list will discover that their mail is all being blocked and stop querying the list causing this. In principle, this should work. But in practice it really does not because many people querying lists are not doing it as part of a pass/fail delivery system. Many lists are queried as part of a scoring system.
Maintaining a DNSBL is a lot of work and after years of providing a valuable service, you are thanked with the difficulties with decommissioning the list.  Popular DNSBLs like the AHBL list are used by thousands of administrators and it is a tough task to get them to all stop using the list.  RFC6471 has a number of recommendations such as increasing the delay in how long it takes to respond to a query but this does not stop people from using the list.  You could change the page responding to the site to advise people the list is no longer valid, but unlike when you surf the web and come across a 404 page, a computer does not mind checking the same 404 page over and over.
Many mailservers, particularly those only serving a small number of users, are running spam filters in fire-and-forget mode, unmaintained, unmonitored, and seldom upgraded until the hardware they are running on dies and is replaced. Unless they do proper liveness detection on the blacklists they are using (and they basically never do) they will keep querying a list forever, unless it breaks something so spectacularly that the admin notices it.
So spread the word,