To get Yahoo Mail Beta, just switch your content preference to Germany, France or UK. Then you will be asked if you want to join the beta when you log into your Yahoo Mail. Say yes, and join the beta.
Then from the options menu, change your content preference to what they were before. Then go to Yahoo Mail again. You should still see Yahoo Beta. If you don’t see it, go to options and click the “Try Beta? button. That’s all.
How to change your content preference:
If you need to enter a valid zip here are some for Germany: 45130 Essen, 12159 Berlin, 16356 Berlin
Update: Yahoo is currently not offering beta access to their Yahoo Mail product. While it is likely that the developers are constantly testing improvements, new features and changes internally. Yahoo users who are interested in new beta opportunities should check out the Yahoo Mail Blog regularly as it is covering those announcements when a new beta is available.
There you find other information as well, including changes that the developers have implemented into Yahoo Mail, or tips and tricks to get the most out of the service.
The last public beta, from what we can tell, landed in 2010. It is not really clear if Yahoo changed the company's policy in regards to public beta releases in the meantime, or if there were simply not enough new features to test, or no need to test them.
Update: Yahoo Mail has recently introduced a redesign of its mail interface to all of its users. The company announced that it will retire mail classic and all other previous versions of Yahoo Mail in mid 2013.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.