You may notice that all of a sudden you can recieve mails but cannot send. Outlook will popup a message saying ‘
Outlook data file cannot be accessed (error 8004010F)‘.
Thou the PST files are there and accessible, the only way to fix this is to re-create your Outlook Profile from the Control Panel by:
Open Control Panel
Open Mail 32-bit
Click on Show Profiles
Select the profile in question
Now open Outlook and reconfigure the account. This should fix the problem (4428)