Plus Addressing email addresses in Microsoft 365

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.

A user with the email address of username@domain.com.au can use the plus addressing feature to extend their email address to username+tag@domain.com.au and all emails sent to the username+tag@domain.com.au email will land in the user's username@domain.com.au inbox. The "tag" can be unique, allowing users to generate an infinite amount of custom email addresses, which they can give out to companies in newsletter sign-up forms, contact forms, and other online forms. Once emails arrive in the user's inbox, the owner can see where the email came from by the email address the sender used. Now the user that subscribed to my newsletter can now easily distinguish my newsletter emails and there are many advantages for doing this.

• The user does not have to contact the IT department to create an alias mailbox.

• The user can create an infinite amount of email addresses and easily do it themselves.

• Custom message rules can easily identify incoming emails.

  • For example, if a company refuses to remove you from there mailing list you can create a message rule to automatically delete the tagged email address.

• Identify companies that are sharing your email address with other companies.

  • For example, if you start receiving emails from a company that is using an email address tagged to another company, you know the company you gave the email address to has shared your details.

This feature is also available with Microsoft's outlook.com and hotmail.com email services For more information please read Microsoft Docs Plus Addressing in Exchange Online.

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Plus addressing: New disable setting and on by default

Plus addressing support in Exchange Online was released in September 2020 as an opt-in feature due to its incompatibility with some preexisting addresses used by customers. New customers had the feature enabled by default and last year we announced that we would be moving ahead with the plan to turn the feature on for all customers.

That Message center post (MC276028 August ’21) generated a fair amount of feedback from customers who do not intend to allow their users to utilize plus addresses. Considering the feedback, we announced that we would implement a new setting to allow customers the ability to disable the feature ahead of the change. That setting is now ready for use, and we are giving customers 30 days to proactively opt out of the feature before we enable plus addressing by default.

Key points: • Timing: begin mid-April and expect to complete by the late May • Control: via Exchange Online PowerShell • Action: make configuration changes to ensure expected experience

How this will affect your organization: Plus addressing will soon be on by default. If you don’t disable plus addressing, your users will be able to utilize plus addresses after the feature is enabled. The new setting is DisablePlusAddressInRecipients in the Organization Config. To opt out of plus addressing, run the following command in an Exchange Online PowerShell session:

Set-OrganizationConfig -DisablePlusAddressInRecipients $true

The setting will only start working when we enable plus addressing for all customers. We plan to roll out that change after the 30-day notice period expires in mid-April. That change will remove the old AllowPlusAddressInRecipients setting and plus addressing will start working for all customers unless they have set DisablePlusAddressInRecipients to True.

What you need to do to prepare: To avoid plus addressing becoming available to your users, admins should set the disable setting to True within the 30-day notice period. Customers with addresses containing pluses may also experience disruptions to deliveries.

Please see Plus Addressing in Exchange Online to learn more.