As of May 2022, plus addressing (also known as subaddressing) is enabled by default in Exchange Online. Subaddressing is an industry-defined way to support dynamic, disposable recipient (not sender) email addresses for mailboxes.
An SMTP email address uses the basic syntax:
<local-part>@<domain>. For example, email@example.com.
Plus addressing uses the syntax:
<local-part>+<tag>@<domain>. For example, firstname.lastname@example.org.
The original email address must be valid. The
+tag value that you add is arbitrary, although regular character restrictions for SMTP email addresses apply (for example, no spaces).
Plus addressing can be used in any email client that sends emails and you can receive emails addressed to you using plus addresses as you would normal emails.
If you create a mailbox with an address that contains a
+ in Exchange Online, Exchange Online will try to resolve the full email address (for example, email@example.com) to a known mailbox. If the first resolution attempt fails, Exchange Online does a second attempt to resolve the email address without the plus sign and tag (for example, firstname.lastname@example.org).
If inbound internet email for your on-premises organization is routed through Exchange Online, your on-premises mailboxes can also use plus addresses if those mailbox addresses are known in Exchange Online. If the on-premises mailbox addresses are unknown to Exchange Online, plus addressing won't work and message delivery will be affected.
Disable plus addressing in Exchange Online
Use the new Exchange admin center to disable plus addressing
In the new Exchange admin center at https://admin.exchange.microsoft.com, go to Settings > Mail flow.
Select Turn off plus addressing for your organization, and then select Save.
Use Exchange Online PowerShell to disable plus addressing
Connect to Exchange Online PowerShell.
The command uses the following syntax:PowerShell
<$true |="|" $false="$false"> " style="box-sizing: inherit; outline-color: inherit; font-family: SFMono-Regular, Consolas, "Liberation Mono", Menlo, Courier, monospace; font-size: 1em; direction: ltr; border: 0px; padding: 0px; line-height: 1.3571; display: block; position: relative;"Set-OrganizationConfig -DisablePlusAddressInRecipients <$true | $false> </$true>
To disable plus addressing in your organization, run the following command:PowerShell
Set-OrganizationConfig -DisablePlusAddressInRecipients $true
Using plus addresses
You can create new plus addresses by adding a new tag. You can use plus addresses as unique addresses for services that you sign up for. You cannot, however, send from plus addresses.
Some web forms don't support plus signs in email addresses.
If you need to unsubscribe from an email list subscription service, some subscription services require that you use the original email address that you subscribed with. You can't unsubscribe by sending an email from a plus address.
As plus addresses are not aliases that are configured on the mailbox, they don't resolve to a user's name in Outlook clients. This limitation results in plus addresses being easily identifiable in the
CC fields of messages. However, there might be scenarios where you can't use a plus address for a Microsoft service that needs to be associated with your mailbox.
To automatically identify and filter messages that are sent to plus addresses, use Inbox rules to act on those messages. Using the condition Recipient address includes, you can specify an action for messages sent to a particular plus address. For example, you can move messages sent to a plus address to a folder.