Office 365 is encrypting emails and you want to turn off this function.
This is not a default function so verify that the encryption is not needed before turning it off.
Disable the encryption by Keyword rule.
- Log into your Office 365 account with administrative rights.
- Navigate to the Exchange Dashboard
- On the Dashboard of the Exchange Admin Center Under Mail Flow select rules
- You will now see the rules for mail flow
- Find the rules that are associated with the Keyword encryption and uncheck them to disable them.
- Send a test email to verify that the encryption is off.