None of the users are able to attach files with an e-mail irrelevant to file type or size. It comes with error message "Operation failed". However able to receive e-mail attachments without any problem:
Windows 2000 server,
Outlook 2003, 2007.
We have recently moved the exchange database to different hard drive b'coz were running out of space on C: drive. May be its got something to do with this problem.