I Recently come across and found there is no solution mentioned by MS or any blogger on the internet.
Here is the solution regarding this concern which can be apply to any M365 Tenant who ever does not want this feature to in place. As many users do not want.
Due to DLP policy already in place for MailTip and Mailflow rules to stamp header on emails.
Let understand What is Email First Contact Safety TIP in MS??
It’s a Default MailTip from MS which is enabled for every M365 Tenant. This comes up when ever you as a recipient receive an email from the sender 1st time.
Biggest question is can this be disabled??
Yes, it can be. Wherein I did lot of research and every where people talking about this is default and can’t be disable. MS bloggers and MVPs stated the same.
But I have the solution in regard to it.
How to solve this problem, we need to make 2 changes on the organization level to fix this:
1: Change in Inbound SPAM Policy in Office 365.
Goto Security portal > Policies & rules > Anti-Spam Inbound Policy
Turn of the circled option in the below image:
2: Along with the above configuration we need to disable 1 more option.
Go to Security portal > Policies & rules > Anti-phishing.
Turning these 2 features will disable the MailTip from Outlook.
Thanks & Regards