Event ID - 1023

Event Id1023
SourceMSExchangeIS Mailbox Store
Description<user name> was validated as <user name> but was unable to log on to <server name> on database "<name>". Error: <error code>
Event InformationThis user does not have the appropriate logon permissions. Configure permissions for this object.

This information from newsgroups may help:
You might get this event when user credentials used to logon to mailbox are wrong. Make sure user speicifed in the description is using correct username and password when logging into his mailbox from outlook.
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