I came across a few great articles from years gone by that really help highlight the importance of the IBM AS/400 in the history of Lotus Domino and vice versa. Below are a few points that may be of interest to you.
At Lotusphere 1999, only 11 months after IBM supported Lotus Domino on the AS/400, IBM sold "$500 million dollars in AS/400 hardware with Domino running native on it, and more than 20,000 licenses of Domino (server) on the AS/400."
"Twenty-five percent of the customers running Domino native on the AS/400 are new to the AS/400 market." The AS/400 had been sold for 10 years at that point, yet it had a 25% increase in new sales that year for systems that primarily facilitated Lotus Domino workloads.
In 1998, Lotus Domino only ran on AS/400's with NorthStar and Apache processors, so pre-1997 AS/400's were not an eligible platform.

At that time, IBM sold more Lotus Domino for AS/400 than on
all flavors of Unix combined.
And at that time, in just 9 months of launch, the AS/400 grew to the 2nd most popular platform to run Lotus Domino.
There was a reason why the AS/400 model 170 Dedicated Server for Domino came with yellow livery. The 170 was known to IBM by the code name "Invader," which was incredibly fitting since it displaced many servers that would be deemed redundant or unnecessary.
Even IBM found simplicity and cost savings in switching:
"In 1997, the AS/400 Brand IT department had 50 PC servers, and there were around nine administrators. They would come in at 2 a.m. when one of those PCs failed and restart it, because that's what had to be done. And when a fix was needed for the PCs, they'd have to put it on all 50 of them, which is a real pain. In 1998, during the Domino for AS/400 launch, they migrated those 50 PC servers to three AS/400s. They went from nine full-time administrators to four part-time."
With the yellow stripe, the user community affectionately dubbed it "Bumblebee." IBM followed suit with the 170's replacements, the iSeries models 270 and 820 Dedicated Servers for Domino, by also giving them a slick yellow stripe.
In 2000, it was stated that in the last two years, Lotus Domino accounted for 25-30% of new AS/400 sales. These are customers who have never had an AS/400 before.
This is impressive food for thought and the early results of a tremendous pairing. The reasons why Lotus Domino on AS/400 made sense in 1998 makes even more sense why IBM Collaboration Solutions products are a great fit on IBM i on Power Systems in 2012 and beyond. The security, scalability and simplicity remain unrivalled.
Additional sources for information here:http://www2.systeminetwork.com/nwn/printstory.cfm?ID=7372http://www2.systeminetwork.com/news/nwn/printstory.cfm?ID=15712
Read the original at Steve Pitcher.