Office 365 Exchange Delivery Issue

[scottkot]

Hello All!

We have a 3rd party vendor that sends out emails utilizing our domain to our customers. These emails still are getting delivered but they are not getting delivered to our own internal email accounts.

i.e. if our 3rd party sends a report to us and our customer, our customer gets the report but we do not. Not in junk either.

This has been working for over 6 years now it is not... thoughts? Thank you.

[#2]

@scottkot Hello, have a message trace been done to see what's going on? https://admin.exchange.microsoft.com/#/messagetrace 

[#3]

@scottkot

Do you have any security mechanisms in place to prevent external partners/servers from sending mails on your behalf? In the meantime, M365 provides protection against so-called "fake CEO" attacks (ATP Anti-Phishing Policies).
Here is a short excerpt: Prevents the specified domains from being impersonated in the message sender's domain. For example, all domains that you own (accepted domains) or specific domains (domains you own or partner domains). This list of sender domains that are protected from impersonation is different from the list of recipients that the policy applies to.