Our sales support team is sending emails using the Marketo plugin for Outlook. For several of the emails that have been sent via send and track, we receive an undeliverable notice from Outlook (see below - note: I've removed the contact information for privacy).
This would lead us to believe that the email has not been sent, but when I check the contact record in Salesforce it shows that the email has been opened.
Has anyone ever encountered this or does anyone have any insight on this topic? Could it be that when Outlook marks an email as undeliverable Marketo somehow thinks it's been opened by the recipient? Or perhaps, the email is actually being delivered and it's an error within Outlook?
Any feedback is appreciated! Thanks,