After upgrading to 2.0.1 & 2.1 on my 3G, I lost the display of all my Yahoo/SBC Mailboxes but my Inbox, Trash, and Sent. Tried Searching this forum (and the net) for a fix, but could not find any relevant info on it.

So I thought I would post the fix for those like me who may have this problem:

1). Enter Setttings>General>Reset, and select "Reset Network Settings".
2). Delete & re-Add each of your Mail Accounts.
3). Enter the "Inbox" of each of them and select "Edit"
4). Select a mail item and then select the "Move" tab.
5). It should now display all folders in the Move screen.
6). Exit out of "Move", go to the account screen, and all should display.

(May not need to do the "Move" steps, but when I entered my SBC mail account, they did not show immediately.... so I did the "Move" steps, they then all appeared)