Office 365 – add extra mailboxes (for free)

I recently decided to completely overhaul my email and passwords to all major sites after getting tired of the relentless spam I received to the account I have had for the past 20 years or so. Additionally my email and (admittedly very old) passwords showed up on Have I Been Pwned? so I thought it was time for a clean break. This is no small undertaking as you can probably imagine but the first step is to sort out your email account. Most importantly though, you still need to be able to receive email to your old address and in some cases, still be able to send from the old account.

Of course you can just add your old address as a secondary email account so you still receive email to that address but I wanted to use the old account as a filter to the hundreds of sites who insist on sending me crap every day which I don’t especially want to read.

Anyway, in my case, I want to create a new email address (mailbox) as a primary address and have a secondary mailbox for my old email address plus another for my business email address. I also wanted to be able to send from these accounts as though they were my primary email if I wanted to. Please note, by secondary mailbox, I am in effect talking about a shared mailbox for which you will have exclusive access to receive and send mail. A secondary mailbox requires no further licence.

The setup

  1. IMPORTANT: Backup your current inbox to a PST file. You can do this by selecting File | Options | Advanced | Export button | Export to a file | Next | Outlook Data File (pst). Ensure you select the correct Inbox from here and click Next. Enter a path for the PST file and click Finish.
  2. In the Microsoft 365 admin center go to Settings > Domain. Ensure the new domain you need is in a healthy state. If not, click on the domain and follow the instructions to make sure it is healthy before proceeding further.
  3. Open up the Exchange admin center and go to dashboard | recipients | shared. Click the ‘+ ‘ sign as below
  1. This will open up the New shared mailbox dialogue. Add your name and your NEW email here. Click the + sign at the bottom and add yourself as a user with permission on the mailbox
  2. Go to dashboard | recipients | mailboxes and select Convert to shared mailbox on the right hand pane.
  3. Click on the shared heading at the top to return to the list of shared mailboxes. Select your NEW mailbox and select Convert to regular mailbox on the right pane.
  4. Open the shared mailbox(es) dialogue by double-clicking on it/them. Click email address. Ensure your new email address doesn’t appear in the list here. The mail address under SMTP is your default address for that mailbox.
  5. Click mailboxes in the toolbar at the top and ensure your new email address is listed there. Sometimes there is a short wait for the mailbox to appear.
  6. Ensure Outlook is closed. Open the mail applet in Control Panel and add your new email address here. After it has resolved and appears in the applet, click Set as Default. I found that I had to actually remove the old email account and re-add it but you may have a different experience here.
  7. Open Outlook and you should see your new account. Click File | Add Account and add your (now secondary) mailboxes to Outlook. Assuming you have given these appropriate permissions in Exchange admin center, you should now be able to add the address of this/these extra shared mailbox(es) in the From field of Outlook and send as that account if you wish. You new account should now default. To be sure you can go back to Microsoft 365 admin center | Settings | Domains and ensure your preferred new email account is set as default there if it isn’t already.

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