In the late 1990's I worked at a large bank's Online Retail Banking website running Netscape's iPlanet webserver on Unix (AIX). Being ~25 years ago, I'm a little foggy on the technical details but at a high level we started getting complaints from customers running IE having trouble connecting to our website. The reps from Microsoft blamed iPlanet, said it worked fine with Microsoft's IIS webservers, and had almost convinced the bank's senior management to simply replace iPlanet with IIS as it would be the trouble-free webserver for use with the most popular browser, IE.
Nobody on the tech team wanted that so we launched into a major tracing & debugging effort and eventually found that a change in IE caused it to start doing the SSL handshake slightly different if it thought it was connecting to a non-IIS webserver. Netscape provided a patch and we were able to keep iPlanet on our beefy Unix servers instead of migrating to a farm of IIS servers on tiny Windows servers (they weren't all that powerful in the 90'). This was about the time that the DoJ was going after Microsoft for non-competitive practices. I recall that someone on our team sent an email to DoJ telling them of our experience, but I don't think they ever got a reply.
Nobody on the tech team wanted that so we launched into a major tracing & debugging effort and eventually found that a change in IE caused it to start doing the SSL handshake slightly different if it thought it was connecting to a non-IIS webserver. Netscape provided a patch and we were able to keep iPlanet on our beefy Unix servers instead of migrating to a farm of IIS servers on tiny Windows servers (they weren't all that powerful in the 90'). This was about the time that the DoJ was going after Microsoft for non-competitive practices. I recall that someone on our team sent an email to DoJ telling them of our experience, but I don't think they ever got a reply.