It’s an often used feature of Gmail to append a ‘+’ (plus) to an email address to create an unlimited number of instant email aliases – see Gmail Blog for an explanation. I gather this is also a feature of Outlook.com, but the same does not apply for hosted domains on Office365. The same can however be achieved with a bit of configuration.

Go to Exchange Admin Centre > mail flow > rules and create a new rule as follows:

Create this rule… The sender is located… Outside the organization

and The recipient address matches… ^yourname\+[\w-]+@yourdomain.com

(For example, if your usual email address is david@yourdomain.com then the rule should match ^David\+[\w-]+@yourdomain.com)

Do the following… Redirect the message to… <select your user>

(The [\w-]+ regular expression will match one or more alphanumeric or hyphen characters).

Next choose the ‘external domains’ tab, select your domain and make sure that the domain type is set as an Internal Relay.

Now that this domain is an internal relay, we’ll need an extra rule to bounce email addressed to unknown recipients more gracefully (instead of looping internally).

Add this as your last mail flow rule:

Create this rule… The sender is located… Outside the organization

Do the following… Reject the message with the explanation… ‘User unknown’

Except if… The recipient is a member of… <select all the valid users>

You will now receive email addressed to david+anything@yourdomain.com in your regular inbox.