A few years ago I had a client that insisted on using yahoo. He had been using the yahoo "build your own" tool for a few years and just wanted me to build a site (using CMSB) but place it on his existing yahoo account. He also used them for email etc. and just wanted everything to stay together.
During the couple of months that I build the site on his yahoo servers everything seemed normal. Right before I was ready to make the live switch, yahoo business services merged with an oversees company called alibaba. I started to notice that I would get an error message pretty frequently, but the client wanted to go ahead and go live with the site. For about a year i would get an error about 50% of the time when I tried to go to the site. I spent many dozens of hours trying to resolve the issue. I checked every single setting I could find, googled everything I could think of, spent probably 8-10 hours on with yahoo "support" (at least half of which was waiting for them to connect me to a live agent). I re-downloaded CMSB and reinstalled everything from scratch and had the same issues as before.
I transferred the entire site to my own hosting and was instantly problem free. It's been 2 or 3 years since then so I don't remember more details than that... but I spent upwards of 30+ hours and could not get yahoo business hosting to work with cmbs.
As a side note... their "support" was literally terrible. I would spent 45-60 minutes waiting to connect, then get asked questions like "have you tried using a different computer?" or "try rebooting your internet service".
Greg Williams