An Outlook user, KT, wanted to defer delivery of messages sent after 6PM, sending them at 7 AM the next day. This is possible to do using an ItemSend macro.

If it's after 6PM or before 7AM, the message is held until 7AM, then sent. Because this is an Outlook script, it only works in Outlook. It will not affect messages sent using smartphones or other devices.

"Set a default 'Do not Deliver before' time" and "To delay sending a message in Outlook"

May 6 2017: Edited the macros to properly move early morning messages ahead a few hours, not 1 day and to account for messages sent Sat or Sun.

Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)

' If after 6PM
  If Now() > DateSerial(Year(Now), Month(Now), Day(Now)) + #5:59:00 PM# Then
    SendAt = DateSerial(Year(Now), Month(Now), Day(Now) + 1) + #7:00:00 AM#
' If before 7AM
  ElseIf Now() < DateSerial(Year(Now), Month(Now), Day(Now)) + #6:59:00 AM# Then
    SendAt = DateSerial(Year(Now), Month(Now), Day(Now)) + #7:00:00 AM#
  End If
 Item.DeferredDeliveryTime = SendAt

End Sub

If you need to skip weekends (or other days of the week), check the name of the day and add additional time to the SendAt time.

Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim dayname As String

' If after 6PM
  If Now() > DateSerial(Year(Now), Month(Now), Day(Now)) + #5:59:00 PM# Then
    sendat = DateSerial(Year(Now), Month(Now), Day(Now) + 1) + #7:00:00 AM#
' If before 7AM
  ElseIf Now() < DateSerial(Year(Now), Month(Now), Day(Now)) + #6:59:00 AM# Then
    sendat = DateSerial(Year(Now), Month(Now), Day(Now)) + #7:00:00 AM#
' We'll test the date of all messages
 ElseIf WeekdayName(Weekday(Now())) = "Saturday" Or WeekdayName(Weekday(Now())) = "Sunday" Then
   ' this will be changed by the next part if a weekend
   sendat = DateSerial(Year(Now), Month(Now), Day(Now)) + #11:00:00 PM#
 End If

dayname = WeekdayName(Weekday(sendat))

Select Case dayname
Case "Saturday"
    sendat = DateSerial(Year(Now), Month(Now), Day(Now) + 2) + #7:00:00 AM#
Case "Sunday"
    sendat = DateSerial(Year(Now), Month(Now), Day(Now) + 1) + #7:00:00 AM#
End Select
    Item.DeferredDeliveryTime = sendat
Debug.Print Now(), dayname, sendat

End Sub

Only Delay message Sent to Specific Addresses

Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)

Const PR_SMTP_ADDRESS As String = "http://schemas.microsoft.com/mapi/proptag/0x39FE001E"

Set recips = Item.Recipients
 For Each recip In recips
 Set pa = recip.PropertyAccessor
 
 Address = LCase(pa.GetProperty(PR_SMTP_ADDRESS))
 lLen = Len(Address) - InStrRev(Address, "@")

 Select Case Right(Address, lLen)
' add additional addresses as neeed, using quotes and comma separator
    Case "mcarnar@domain.com", "bburns@domain.com", "rchildars@domain.com", "curry@domain.com"
         
    Case Else ' remove case else line to be warned when sending to the addresses
     strMsg = strMsg & " " & Address & vbNewLine
 End Select
 Next

' using <> delays these addresses only; 
' use = to delay all but these addresses

If strMsg <> "" Then
' If after 6PM
  If Now() > DateSerial(Year(Now), Month(Now), Day(Now)) + #5:59:00 PM# Then
    SendAt = DateSerial(Year(Now), Month(Now), Day(Now) + 1) + #7:00:00 AM#
' If before 7AM
  ElseIf Now() < DateSerial(Year(Now), Month(Now), Day(Now)) + #6:59:00 AM# Then
    SendAt = DateSerial(Year(Now), Month(Now), Day(Now)) + #7:00:00 AM#
  End If
Item.DeferredDeliveryTime = SendAt
 
End If
End Sub

How to use the macro

First: You will need macro security set to low during testing.

To check your macro security in Outlook 2010 or 2013, go to File, Options, Trust Center and open Trust Center Settings, and change the Macro Settings. In Outlook 2007 and older, it’s at Tools, Macro Security. If Outlook tells you it needs to be restarted, close and reopen Outlook. Note: after you test the macro and see that it works, you can either leave macro security set to low or sign the macro.

Now open the VBA Editor by pressing Alt+F11 on your keyboard.

To use the macro code in ThisOutlookSession:

1. Expand Project1 and double click on ThisOutlookSession.
2. Copy then paste the macro into ThisOutlookSession. (Click within the code, Select All using Ctrl+A, Ctrl+C to copy, Ctrl+V to paste.)
   

More information as well as screenshots are at How to use the VBA Editor.