Level 10
"Microsoft is adding support for custom email addressing to Office 365 email services, a feature it hopes to complete in Q3 2020.
Custom email addresses are an optional feature that some email providers can support. The feature is described in the RFC 5233 internet standard.

Officially known as subaddressing, this standard allows users to extend their email address using "tags" or the plus (+) character, hence its two alternative names of tagged addressing or plus addressing.

For example, a user with the email address of can use the plus addressing feature to extend their email address to
If the user's email address supports subaddressing, all emails sent to the email will land in the user's inbox...."