I received the following message on my Android phone whenever I tried to access my Yahoo mail account.
The application PC-mail (process com.android.email) has stopped unexpectedly. Please try again.
This problem happened all of a sudden after the application had been working fine for a long time (since I got the phone). From what I understand, this error message can pop up when the application can’t handle certain email headers. I was able to fix the problem on my phone by going to my Yahoo account online and moving all of my email into another folder (removing it from the inbox). It might be possible to try to guess which email includes the offensive header, and move only that email to another folder, but I found it faster just to move everything. Seems to work fine now.