In Office 365, like in any other hosted exchange service, you can create multiple aliases for your account. You just need to (while logged into OWA, you must have admin rights):
1. Go to Options -> See All Options…
2. Choose Manage My Organization.
3. In Mailboxes section of Users & Groups select your mailbox and click Details.
4. Expand E-Mail Options, click Add, enter your new name for email address, choose domain (if you have more than one), click OK. Now Save.
Voila! You got new alias on which you can receive emails. And that’s the problem, you can only receive. I wanted more. I wanted to be able to send emails from such alias. Fortunately there is solution to that, but not with aliases. You must use groups instead. Repeat two first steps mentioned above and then:
1. In Users & Groups click Distribution Groups.
2. Click New and fill in Display name, Alias, E-mail address. Click Save.
3. Now select your newly created group and click Details.
4. Expand Delivery Management and check Senders inside and outside of my organization. Click Save.
You now have a group which can receive emails from outside of your domain. As you’re the only member of this group you actually have email alias. But you’re still unable to send emails as this group.
What you’ll need to do now is a little more complicated than clicking options in menus, but have no fear it’s not rocket science. Let’s proceed:
1. Go to Start Menu -> Accessories -> Windows PowerShell and launch Windows PowerShell.
2. Type this command “$LiveCred = Get-Credential” and hit enter. It would open window where you need to input your admin credentials to O365.
3. Now you need to execute this command to connect to the service “$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $LiveCred -Authentication Basic -AllowRedirection”. You’ll receive warning message, but don’t be afraid, it’s just telling you that you’ve been redirected to proper server.
4. Execute “Import-PSSession $Session”. To import commands you’ll use to manage your O365 from PowerShell. It can take a while, so be patient.
5. Now is time to give you permissions to send emails as a group. Execute “Add-RecipientPermission “firstname.lastname@example.org” -AccessRights SendAs -Trustee “email@example.com””. You’ll need to confirm it. Of course you need to replace firstname.lastname@example.org with address of your group and email@example.com with your email address in O365 from which you want to send emails as a group.
That’s it. You can now send emails from group’s email address. In OWA you just need to click From when creating new message and if your group is not on the list select Other e-mail address, then double click on given group so it would appear in From field at the bottom and click OK. In Outlook procedure is pretty the same, you’ll just need to select the group from Global Address List.
I find this functionality really useful and I hope that so would you. Enjoy!
UPDATE: There is a better way, you can create shared mailbox. Just follow steps from this link.