How to prevent users sending emails without subject entered in Outlook?

While you send an email through Outlook, in some times, you can send emails without subject entering which maybe is not a good habit. Is there any way to force users to send email with a subject in Outlook?

Prevent sending emails without subject entered with VBA

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Prevent sending emails without subject entered with VBA

There is no way except VBA code to solve this problem.

1. Enable Outlook, press Alt + F11 keys to open Microsoft Visual Basic for Applications window.

2. Double click ThisOutlookSession in the Project1 pane, then copy and paste below code to the blank script.

VBA: Prevent sending email without subject

Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
'UpdatebyExtendoffice20180511
Dim xObject As Object
On Error Resume Next
If Item.Class <> olMail Then Exit Sub
Set xObject = CreateObject("VBScript.Regexp")
With xObject
    .Global = True: .Pattern = "^\x20*$"
    If .test(Item.Subject) = True Then
        MsgBox "No subject entered", vbInformation, "Kutools for Outlook"
        Cancel = True
    End If
End With
End Sub

3. Save the code, now if the email you send without subject, it will pop out a dialog to remind entering subject.

Note: This VBA code work for all accounts in Outlook