RE: Error 0x8004210C
I had the same problem. Here's how I solved it.
Step #1.
I exited Outlook and made a copy of OUTLOOK.PST into another directory just
in case of disaster. I gave it a name of OLD_EMAIL.PST. OUTLOOK.PST is a
hidden
file, so you will have to change your browser or Windows Explorer settings
to show hidden files and folders]
Step #2.
I deleted the original OUTLOOK.PST file.
Step #3.
I launched Outlook. It gave me the error that there was no PST file. As I
hoped, it made a new blank one for me after prompting me for a password.
Step #4.
I verified my email account info, which was all as I had left it. I chose
SEND/RECEIVE email and it synched properly into the new folders.
Step #5.
I used File/Open to open the OLD_EMAIL.PST file. It now appears as a set of
folders under the usual email folders.
The problem with being unable to remove message headers for messages that
were deleted via the webmail interface has completely gone away!
Don Pilcher
Half Moon Bay, CA
(e-mail address removed)