I got the solution in some other site. With the following procedure I am able to send emails without email id in the "From" field.
Sub SendMailCDO(aTo, Subject, HTMLBody, aFrom)
Const cdoOutlookExvbsss = 2
Const cdoIIS = 1
'Create CDO message object
Set Message = CreateObject("CDO.Message")
With Message
'Load IIS configuration
.Configuration.Load cdoIIS
'Set email adress, subject And body
.To = aTo
.Subject = Subject
.HTMLBody = HTMLBody
'Set sender address If specified.
If Len(aFrom) > 0 Then .From = aFrom
'Send the message
.Send
End With
End Sub