| Event Id | 8255 |
| Source | EXCDO |
| Description | The background calendaring agent failed to logon to the MDB, or create a session object on the MDB:<GUID>. The error code is <error code>.The rendering of large calendars with the web client or Microsoft Internet Explorer for the mailbox <mailbox name> with GUID:<GUID> will be slower. |
| Event Information | According to Microsoft: Cause: This event can occur when drive M is being scanned by antivirus software, or is being backed up by backup software. User Action : Check that the Exchange Server directories and drive M are not being scanned by antivirus software. Also ensure that the Exchange Server folders and drive M are not being backed up by any kind of backup application. If the events continue to be generated, make a list of the mailboxes that are affected. This information is available in the description section of the event. You can then export these mailboxes to PSTs and import them back. |
| Reference Links | The background calendaring agent failed to logon to the MDB |
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