I use Yahoo Small Business for my mail. I use the web interface too.
I notice that web links typed to myself don't work.
OK so the text editor in Yahoo has an "Insert Link" icon on the icon bar. It's over to the right and looks like two linked circles.
You have two options with this. You can just click on the icon and it will pop up a dialog box in which you can enter the link. It will then be properly formatted as a hypertext link and send correctly. The second option is that you can type some text, then select the text and click on the link button. This then turns your text blue and hides the link behind what you have written. This is quite similar to how the URL button works here on VV when you put the link on the url side of the brackets with url= and then type the text in between the brackets
UK Google link.
One more step, a pain, I know. But it works and you can use it.
I'm sure they'll get the formatting stuff sorted later. It's usually an indication that something much more serious is not working and they are focusing all their effort on it.