For Exchange Online you can use since September 2020 Plus Addressing. With Plus Addressing your users can create own custom e-mail addresses by adding a suffix to their existing default or alias e-mail addresses.

An SMTP email address uses the basic syntax: @. For example, sean@contoso.com.

Plus addressing uses the syntax: +@. For example, sean+newsletter@contoso.com.

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). For more information about using plus addresses, see Using plus addresses.

By default, plus addressing support is disabled in Exchange Online. Since Exchange Online has always supported regular email addresses that already contain the plus sign, if you enable plus addressing, these email addresses might stop working. See the note below in Enable plus addressing in your Exchange Online organization.

You can’t enable plus addressing in the Exchange admin center (EAC); you can only enable it through Exchange Online PowerShell.

Plus addresses are only supported for mailboxes and Groups. There is partial support for on-premises recipients with hybrid configurations so long as the messages first pass through Exchange Online before being routed to an on-premises server. For example, a message sent from one on-premises mailbox directly to another would not support plus addressing but a message from an external sender would.

Source: https://docs.microsoft.com/en-us/exchange/recipients-in-exchange-online/plus-addressing-in-exchange-online


Connect to Exchange Online
Import-Module ExchangeOnlineManagement
$credential = Get-Credential
Connect-ExchangeOnline -Credential $credential -ShowProgress $true

Check if Plus Addressing is already enabled
Get-OrganizationConfig | fl Allow*

Enable plus addressing
Set-OrganizationConfig -AllowPlusAddressInRecipients $true




Links

Plus Addressing in Exchange Online
https://docs.microsoft.com/en-us/exchange/recipients-in-exchange-online/plus-addressing-in-exchange-online