Enable '+' plus addressing in Exchange Online

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What is '+' plus addressing?

Plus addressing is an easy way to create many custom email addresses that all go to one mailbox. This is accomplished by adding a suffix to a standard email alias (the local-part before the @ bit).

Let's look at an example:

Default email address - [email protected] [local-part]@[domain]

Sample '+' plus address - [email protected] [local-part]+[tag]@[domain]

The plus symbol is treated as a special indicator where Exchange will ignore everything after it (up to the @ symbol) and deliver all mail to the default SMTP address. So in the example above, all mail sent to [email protected] will be delivered to [email protected].

Plus addressing and Microsoft 365

Sounds great, but why is it not enabled by default in Exchange Online? Alas, there is a good reason. The '+' sign according to RFC is actually a valid part of an email address. So it's possible that some organisations are already using it in their email addresses.

Example:

If plus addressing was enabled, where do you think the mail for the shared mailbox would be delivered?

Check if you have any affected email addresses

Just imagine turning on plus addressing and suddenly mail starts to go to unintended mailboxes! Before we go and enable the feature, we should check if we have any email addresses in our organization with a plus already in them.

Connect-ExchangeOnline Get-Recipient | Where {$\_.EmailAddresses -like "\*+\*"}

If nothing is returned, then you're probably fine to enable plus addressing in your tenant. Of course, you might need to take it through change control...

Enable '+' email addressing via Exchange Online PowerShell

Luckily, enabling the feature is straight forward and can be done with just one line of code. However, once it's enabled it may take some time before it takes effect across your entire tenant.

Limitations - Currently, plus addressing only works for mailboxes. Support for non-mailboxes such as groups and distribution lists will be available by the end of December 2020. See comments in the original user voice forum post (TLDR: there was a bug, so the initial feature release was scoped).

Connect-ExchangeOnline # Check current setting to see the status Get-OrganizationConfig | FL AllowPlusAddressInRecipients # Enable the feature by setting AllowPlusAddressInRecipients to true Set-OrganizationConfig –AllowPlusAddressInRecipients $true

Enable '+' plus addressing in Exchange Online

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What is '+' plus addressing?

Plus addressing and Microsoft 365

Check if you have any affected email addresses

Enable '+' email addressing via Exchange Online PowerShell

Shout about it from the rooftops

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Comments

More from this blog

What is '+' plus addressing?

Plus addressing and Microsoft 365

Check if you have any affected email addresses

Enable '+' email addressing via Exchange Online PowerShell

Shout about it from the rooftops