A couple of times I've sent emails with blank subject line unknowningly.
Blank subject emails are often blocked or filtered.
For Outlook 2007, and perhaps 2003, there doesn't seem to be a warning pop-up upon sending an email with an empty subject line.
Solution: (Thanks to Ankit Jain)
Need to write macro in Visual Basic editor (Alt-F11) -> Microsoft Office Outlook->ThisOutlookSession (double click) and paste code below to right panel.
For MS Outlook 2007 (Works)
Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim Answer As String
If IsNull(Item.Subject) Or Len(Item.Subject) = 0 Then
Answer = MsgBox("Subject field is empty. Do you still want to
send the e-mail? ", vbYesNo + vbQuestion, "Missing subject")
If Answer = vbYes Then
Cancel = False
ElseIf Answer = vbNo Then
Cancel = True
End If
End If
End Sub
For MS Outlook 2003 (I have not tested)
Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim strSubject As String
strSubject = Item.Subject
If Len(strSubject) = 0 Then
Prompt$ = "Subject is Empty. Are you sure you want to send the Mail?"
If MsgBox(Prompt$, vbYesNo + vbQuestion + vbMsgBoxSetForeground, "Check for Subject") = vbNo Then
Cancel = True
End If
End If
End Sub