This week I received a new subscription to my newsletter and I noticed the email address looked a tad strange. The email address contained +powerassist which I instantly knew would not be part of someone's official email address.
After a bit of research I found out that Microsoft had introduced support for custom email addressing with Microsoft 365 email services. This is commonly known as Plus Addressing and is a standard that allows users to extend their email address using "tags" or the plus (+) character.
"Every day Basic Authentication remains enabled in your tenant, your data is at risk, and so your role is to get your clients and apps off Basic Authentication, move them to stronger and better options, and then secure your tenant, before we do."
Microsoft Exchange Team