Outlook 2016 (Office 365 Home) - Edit or Customized SMTP Header for ALL outgoing mail

Question

The situation:

Office 365 Home installed on Windows 7 - 64 bit. Outlook is configured to connect to GoDaddy POP e-mail account. Incoming uses GoDaddy server, Outgoing uses Mandrill.

When emails are sent from Outlook, with multiple recipients in either "TO" or "CC" fields - recipients are stripped from "TO" and each recipient is unaware they were CCd along with others.

Some research points to Mandrill's need for a "custom line" in the "SMTP Headers" - found here - which is this:

X-MC-PreserveRecipients: true;

This change will "preserve recipients" in the headers of the email, so that all CC'd peoples will be aware of the CC and can reply to the group chain.

After 30min on the phone with Microsoft Support, no technician at any level could give me information on editing or customizing the SMTP Headers.

There is an outdated 2010 extension that I found on this site, but does not work with newer versions of Outlook.

Can anyone please tell me how to edit, view, or customize the SMTP Headers for ALL Outgoing mail in Outlook 2016 (via Office 365 Home)

Eric Legault Eric Legault · Accepted Answer · 2017-03-06T01:29:03

You can add headers to all outgoing emails by using VBA or an add-in and trapping the Application.ItemSend event. Use the PropertyAccessor object and call the SetProperty method, like this:

Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim objEmail As Outlook.MailItem
Dim objPA As Outlook.PropertyAccessor

Set objEmail = Item
Set objPA = objEmail.PropertyAccessor

objPA.SetProperty "http://schemas.microsoft.com/mapi/string/{00020386-0000-0000-C000-000000000046}/X-MC-PreserveRecipients", "true"
objEmail.Save()

End Sub

Outlook 2016 (Office 365 Home) - Edit or Customized SMTP Header for ALL outgoing mail

1 Answers