Question: My Exchange Server 2003 (running on Windows Server 2003) fails at around 04:54 on a regular basis, though not necessarily every day.

By "fails" I mean that my colleagues try and check their emails and Outlook says "outlook is not connected to exchange." Since outlook tries to update the email every 3 minutes or so, and it records the time when the folder was last updated, it is possible to see the time of failure.

It is impossible to download emails until the server is restarted. Thereupon everything works well.

I have looked in Scheduled Tasks and can't see anything pertinent.

Does anyone have any ideas?

Answer: 
**Question:**

a) What version of exchange 2003 are you using ? Standard or Enterprise 

b) Is this part of SBS2003 or a stand alone exchange.

**Suggestions:**

1) Can you navigate to this path in registry.

HKEY\_LOCAL\_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\Server name\Private-Mailbox Store GUID

Check if you have a key called 
*Database Size Limit in Gb*
and what's the value there.

2) Whats the DB size on disk?
Default priv1.edb path is c:\Program Files\Exchsrvr\MDBDATA

**Possible Causes:**

a) Exchange 2003 DB is dismounting because of 18GB hard limit for Exchange 2003 standard.
This is usually resolved by increasing the db size limit to 75GB for Ex03 Standard. 

ref:
<http://support.microsoft.com/kb/912375>

White-Space / Offline Defrag's etc, to reclaim space:
<http://www.msexchange.org/tutorials/exchange-isinteg-eseutil.html>
Try looking in the Event Viewer if something occurs around the time it fails each time. 
Hit Start -> Run -> type eventvwr in the Run box to open the Event Viewer, check the events under System and Application logs.
In addition, if you have a monitoring application such as HP openview or Centerity you can create a business service which will include all components that are required for the server to run, such as disk, cpu, memory monitors as well as networking, storage, application monitors, through that you will be able to identify the source for the server’s fail on that specific time when it fails.