First you need to download newest version of Webmail and the Yahoo Webmail Extension from here and save on your desktop
Now open your thunderbird go to Tools-> Addons->Installs and install .xpi files we have downloaded in the above step after installing restart thunderbird.
Once you open thunderbird go to File->New->Account
Check "Email account" and click next
Fill in Email address "email@example.com" and click next
Check "Pop" and make your incoming server 127.0.0.1 click next
Incoming Username "firstname.lastname@example.org" and click next
Name your thunderbird folder whatever you want and click next..
Your account should have been created....now go to Edit->Account Settings
Under your Yahoo email click "Server settings"
Make the Port 1025 and under security settings click "never" (you can fool around with this and see if you can get it to work under other security settings)....also make sure your Username reads "email@example.com"
Then click OK
Lastly go to Tools->Addons again and highlight Webmail and then click Preferences
Make the port in here 1025 as well and then click ok. finally restart thunderbird again.
That's it now try downloading your mails
This seems to be the simple solution
Just go into yahoo mail options and set the preferred content setting to Asia--then you have POP3 enabled for free; currently getting all Yahoo mail in my gmail directly
Check this for detailed instructions from here
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