As most people know, back in the days of Exchange 5.5, Exchange servers were grouped into sites, representing groups of well-connected servers. In Exchange 2000 and Exchange 2003 we introduced the idea of routing groups, which represented well-connected servers, and administrative groups, which represented administrative boundaries.
In Exchange 2007 (aka Exchange 12), our management model has evolved such that we no longer need to expose routing groups or administrative groups. However, because we live in the same Active Directory hierarchy and object model as Exchange 2000/2003, we found that we still needed to create secret admin and routing groups to hold Exchange 2007 servers; groups that would never be exposed to administrators... unless they used legacy management consoles or poked around manually in the Active Directory.
So the question arose, here in the cloistered hallways of the Redmond campus, what should we name these secret groups? They had to be named something, and we had to be sure that we chose a name that nobody with an existing Exchange 2000/2003 deployment had chosen (because we want to be sure that the new groups contain only Exchange 2007 servers); but since they were to be hidden from all but the nosy, they didn't have to be particularly euphonious names.
In fact, as you know if you've performed haruspicy on the Exchange 2007 AD configuration, the names we chose are these:
Exchange Administrative Group (FYDIBOHF23SPDLT)
Exchange Routing Group (DWBGZMFD01QNBJR)
Not, perhaps, poetic. In part, at least, rather mundane. "Exchange Administrative Group". No Pulitzers there. But whence those odd jumbles of letters and numbers?
The original idea had been to append GUIDs to the names to ensure uniqueness. But it was put to us that this was unimaginative, and that if we had any pride we would think of something "clever". So the floor was opened to suggestions.
Some people favored numbers, transcendental or otherwise interesting pi (3.141592654...), e (2.718281828...), phi (1.618033989...). The Hardy-Ramanujan number (1729, the smallest number that can be written as the sum of two cubes in two different ways) was mentioned.
Pop culture references began to appear; 24601 (Jean Valjean's prisoner number), 2716057 and 3370318 (Bender and Flexo's serial numbers, from Futurama). THX1138 (Lucas' trademark) was too obvious to need mentioning.
As the person actually making the change, however, I got final say; and I chose to reject the math and pop culture geeking of my peers in favor of my own. I cast my mind back to 2001 (the novel movie, not the year), and HAL. It was widely asserted that the name HAL had been derived from IBM, by employing a simple Caesar cipher and shifting each letter one space backwards. I resolved that if it was good enough for Arthur C. Clarke, it was good enough for me - and, by extension, good enough for you, the valued customer.
At this point, it should be a trivial exercise to "decode" the hidden message in the admin and routing group names - if a further hint is needed, I'll add that they both decode to the same message. For the lazy or impatient, I'll reveal the answer on the other side of a handful of ellipses.