Yes, indeed - if it was not clearly worded in the email.
“Hello, this is an email to alert you to the fact that your software, Office 365, is vulnerable to spoofing most trusted people in your organisation. Here are the details. Please confirm this in a face to face conversation with your head of security.”
Intent goes a long way… 
Must… not… meme…
Subject: Developers, developers, developers, developers, developers… developers!!!
Bonus points if you send another saying “I… love… securityYEAAAAAAHHHHH”
Linking to this thread every so and again, of why not outlook, gonna necroplomp it here:
Sounds like yet another reason not to use microsoft products…
I’m becoming very anti-microsoft these days. Mostly due to their own purposeful changes to windows over the years. It feels like it’s not getting better, but is only getting worse as they further invade users privacy, give forced ads and seek to monetize users, and push more and more users into their ‘cloud’ subscription based services.
It feels like Microsoft see’s customers as financial cows to lock into cages and milk as much as humanly possible for their cash.
This is why i am refusing to update to newer windows. over the next few years i’m going to learn linux and eventually switch all my machines over.
Microsoft goood, very very goood. YES. 
Good help. Good people. No need for beta testers. Customer is good beta tester for Microsoft. Customer pays Microsoft to beta test for them instead.
Even companies running Micro$hit across hundreds of servers, workstations and terminals are paid-alpha testing their stinking garbage.
Then again, without their endless incompetence, I may be out of a job.