Gmail style ‘plus’ email aliases in Office365

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…┬áThe 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.

Disabling delivery and read receipts in Exchange Online

The default configuration for Office 365’s Exchange server is to automatically respond to requests for mail delivery reports. If like me you don’t want to divulge this information then here is what you need to do.

Follow these steps to block all forms of email delivery and read receipts …

Exchange Admin Centre > mail flow > remote domains > Default 
Untick 'Allow delivery reports' and 'Allow non-delivery reports'
Save
Screenshot 2019-06-07 at 09.38.39.png
 
Next create four separate mail flow rules to remove these mail headers:
 
Disposition-Notification-To
Return-Receipt-To
Receipt-Requested-To
X-Confirm-Reading-To
 
Exchange Admin Centre > mail flow > rules > +
Create a new rule > More options...

Apply this rule if... The Sender is located... Outside the organization
Do the following... Modify the message properties...
Remove a message header (paste a header as above)
Save
You should end up with four rules like these:
 
Screenshot 2019-06-07 at 09.39.06.png
 
Those mail flow rules should strip out the headers and block read receipts before they reach a recipient’s mailbox, but just to be sure:
 
Outlook > Settings > View all Outlook settings > Email
Message handling > Read receipts > Never send a response
Save
Screenshot 2019-06-07 at 10.01.42.png