Sending, receiving, and organizing email in Outlook on the web for business
Just wanted to share some context of the issue you're seeing. See this article: Improvements to tackle spam in Outlook (microsoft365.com)
A couple months ago, "improvements" were added to help protect recipients of email messages.
The "Unverified" warning is listed towards the bottom.
The only way to "fix" or prevent this warning from being shown to a recipient is for the SENDER to take the appropriate actions to properly sign their outgoing emails with the necessary email protections that show the email is from a legitimate & authorized email sender.
Malicious email senders often "spoof" emails so that they appear to come from within your company or a company/business or sender that you know/trust. Checks are made against the emails to ensure these emails are truly from who they say they are. If those protections are not validated during the checks, then you get the warning message. That's a good thing.
If you work at a company with an IT department, and the messages are coming from a system or application that belongs to you or you are partnered with, then your IT staff should be able to implement the necessary email security protections so that they pass the checks.
If the emails are coming from somewhere completely outside your company, then reach out to the sender & let them know they need to properly setup their emails so that they pass the checks.
Of course, the other option is that these are truly not coming from where they say they are & you should heed the warning being presented to you!
Email security mechanisms such as SPF and DKIM are not new. All senders & mail administrators should be utilizing these, especially if they're performing authorized email spoofing (ie, the message says its coming from your company, but, its actually coming from a 3rd party's email system instead).
Just an FYI - I'm just an IT guy myself and don't work for Microsoft. I will NOT be following replies to this message. I just wanted to try to clarify what it is that is occurring w/the Unverified warning message that started appearing recently.