We found a bug where a rule in Content Filtering would apply to all internal senders of a domain. A customer added a rule for sending all "Dr. Oz" spam emails to the Trash folder with the following settings:

Somehow this rule was causing all emails sent internally to go straight to the trash folder for each user. The word "oz" is not in any of their names, their domain name, or business name. Removing the rule stopped this behavior.

 

Just to clarify, to test this I sent emails between a few users containing only "Test" for both subject and body and did not include a signature, attachment, etc.

 

Example:

[2015.12.09] 08:10:29 [56822] Delivery started for sender at 8:10:29 AM
[2015.12.09] 08:10:33 [56822] Skipping spam checks: User authenticated
[2015.12.09] 08:10:36 [56822] Starting local delivery to recipient1
[2015.12.09] 08:10:36 [56822] Delivery for sender to recipient1 has completed (Delivered to Trash) Filter: Dr. Oz
[2015.12.09] 08:10:36 [56822] End delivery to recipient1

[2015.12.09] 08:10:36 [56822] Starting local delivery to recipient2
[2015.12.09] 08:10:36 [56822] Delivery for sender to recipient2 has completed (Delivered to Trash) Filter: Dr. Oz
[2015.12.09] 08:10:36 [56822] End delivery to recipient2
[2015.12.09] 08:10:36 [56822] Delivery finished for sender at 8:10:36 AM    [id:216156822]