Microsoft have made it available to create free mailboxes in Exchange Online 🙂
These mailboxes do not have a Active Directory User attached, so they can only be reached trough other Office 365 MailboxEnabledUsers.
New-Mailbox -Name “NameIT” -Alias NameIT -Shared
This will create a mailbox with your tenant Onmicrosoft.com domain.
Set-Mailbox NameIT -ProhibitSendReceiveQuota 5GB -ProhibitSendQuota 4.75GB -IssueWarningQuota 4.5GB
You’ll have restrict the mailbox to 5GB or it will be terminated, cause thats the limit of a free share mailbox.
Go to Exchange Online Administration and create a security mailenabled group. To make it visable for the Shared Mailbox it have to exist in Exchange Online.
Add the members you would like to gain access to your shared mailbox.
Add-MailboxPermission “NameIT” -User NameITSG -AccessRights FullAccess
This will give your Security Group access to the shared mailbox.
Add-RecipientPermission “Invitation Nor-Fishing” -Trustee invitationnorfishinSG -AccessRights SendAs
This will give your Security Group SendAs access to the shared mailbox.
Last but not least you can change the e-mail address of this Shared Mailbox under Exchange OnlineRecepientsShared. Here it will be listed. You can also change which address you will send from when using this mailbox as sender.