Dim Sender_email As String
    Sender_email = vbNullString

If objMail.SenderEmailType = "EX" Then
    Sender_email = objMail.Sender.GetExchangeUser.PrimarySmtpAddress
Else
    Sender_email = objMail.SenderEmailAddress
End If

Const PR_SMTP_ADDRESS As String = "http://schemas.microsoft.com/mapi/proptag/0x39FE001E"
Dim Sender_PA As Outlook.PropertyAccessor
Set Sender_PA = objMail.Sender.PropertyAccessor
Dim Sender_email As String
    Sender_email = vbNullString

If objMail.SenderEmailType = "EX" Then
    Sender_email = Sender_PA.GetProperty(PR_SMTP_ADDRESS)
Else
    Sender_email = objMail.SenderEmailAddress
End If