I have a real simple function that all it does is Delete messages older than
X days. I'm not sure why, but if I run it once it deletes some of the
messages but not all. With 1000's of messages in the folder it may take 3 or
4 runs for it to finally delete all the messages over X days. Is there some
problem with CDO where it can only process a small number of messages at one
time?

Dim NumDaysToDelete

NumDaysToDelete = 3

CleanMail(NumDaysToDelete)

Sub CleanMail
Dim oSession
Set oSession = CreateObject("MAPI.Session")

strProfileInfo = "cgyex001" & vblf & "ecntrckm"

oSession.Logon "", "", False, True, 0, True, strProfileInfo

Const CdoDefaultFolderInbox = 1 ' uncomment for VBScript code

Dim oFolder
Set oFolder = oSession.GetDefaultFolder(CdoDefaultFolderInbox)

Dim oMessages
Set oMessages = oFolder.Messages
For Each oMessage In oMessages
If DateDiff("d",oMessage.TimeReceived,now) = NumDaysToDelete Then
oMessage.Delete
End if
Next
End Sub