MC276028 – Plus addressing support in Exchange Online was released in September 2020 as an opt-in feature. This was due to preexisting usage of plus signs (+) for email addresses in the service. At the same time, Microsoft made plus addressing on by default for new customers.
With the successful introduction of the feature, Microsoft is now making plus addressing an always-on feature and removing the opt-in setting. Due to legacy mailboxes with email addresses containing plus signs (+), Microsoft is announcing a long notice period to allow customers to transition away from these mailboxes or addresses. This includes mailboxes on-premises.
- Timing: Starting in January 2022, plus addressing will be turned on for all customers and the setting will be removed.
- Action: Retire any email addresses that contain plus signs (+) for hosted and on-premises mailboxes to avoid email delivery disruptions.
How this will affect your organization:
If you don’t stop using email addresses with plus signs (+), Exchange Online may be unable to deliver emails to them when plus addressing is turned on for the entire service.
What you need to do to prepare:
To fix any potential problems, remove any addresses with plus signs (+) from your organizations’ mailboxes.
If you are not blocked from using plus addressing, you can still enable plus addressing for your organization before January.
Review the following to learn more about plus addressing: Plus Addressing in Exchange Online