Specific emails not coming through to Outlook

Question

Outlook 2016 - I'm not receiving emails from specific people (one of which is myself) to my outlook email.  We use mimecast as our mail filter - so I can also access my email in mimecast to see the emails I'm not getting.

When I test and send an email from myself (@domain.com) to myself (@domain.com) the email appears in my mimecast email but not in my outlook.  In mimecast following the email it stays on our internal exchange server and never leaves the domain.  Same goes for specific users inside and outside my business (not that they never leave the domain - but they appear and are allowed through mimecast, but never appear in outlook)

They are not in blocked senders (wrench - options - block or allow from the web browser) and there are no rules effecting these users/emails that I can see from the outlook application - Rules.  

I have uninstalled and reinstalled the office 365 2016 package.

Any thoughts?

Answer 1

Hi Jason,

Thank you for your update. According to the message header you provided, I’d like to confirm if the emails went into Junk Email folder or filtered by mimecast. Also, I’d like to know the results of the suggestions mentioned above if you have tried. This will help us narrow down and process further.

1. If they’re not in Junk Email folder, please contact and consult mimecast support for the detailed situation. 
2. Please let me know whether the emails exist in OWA (Outlook Web App). If so, the issue is probably related with sync.
3. Moreover, to verify if the mimecast filtered the emails, you can try to close mimecast and send test emails if it’s possible.
4. On the other hand, message trace will help us better know where the emails go. Please contact your admin to search these emails and send the report to me.
5. For better know where the emails go, it might be a good idea to run Message trace. If you’re not an admin, please contact admin to run it. And don’t forget to export the result as Enhanced summary report and send me as well.

Regards,

Marvin

Answer 2

Hi Jason,

Thank you for contacting Microsoft Forum Support. Based on your description, if I’m right, you use a third-party mail filter and some emails from specific people cannot be received in your Outlook client. In fact, if the recipients are inside your organization, the emails won’t leave Exchange server. Only when you send emails to people outside your organization, they will go out of Exchange server. Therefore, I suggest you try the following steps and check if it works.

1. Please confirm if the emails are in Outbox or Junk Email folders.
2. If not, you can log in to OWA (Outlook Web App) to check if the emails exist.
3. Since the emails can be found in mimecast but cannot be received in Outlook, the issue is probably regarded with the third-party mail filter. Please confirm if the emails are filtered by mimecast.

Moreover, to confirm where the emails disappeared, please contact your admin to run Message Trace.

1. Use an admin account log in Admin portal, click Security & Compliance icon.
2. In Security & Compliance admin center, navigate to Mail flow > Message trace > Start a trace.
3. In the panel, select the conditions such as sender, recipient, delivery status and time range to search these emails.
4. Please choose Enhanced summary report to download the results and send it to me via Private Message if it’s convenience.

Besides, I'd like to confirm some information regarding this issue.

1. Are the external recipients Office 365 users?
2. Did you receive any Non-Delivery Report (NDR)? If so, please send me the NDR via private message as well. It will help us narrow down.

Regards,

Marvin

Answer 3

Are the missing messages in Outlook on the web (OWA) ?

If you right click on the Inbox folder in Outlook and choose Properties, then Clear offline items, do they show up?