Exchange Online administrators can now recover deleted items from a user or shared mailbox.

To use this new functionality you need to use the new Exchange Administration portal https://admin.exchange.microsoft.com/ and go to the Mailboxes blade

Then either select the mailbox you want to recover deleted items and click on the Recover deleted items button

Or click on the mailbox and click on the Recover deleted items link available under the More action section

Then you can easily browse the delete items dumpster to search and select the item(s) to recover

You can see from there the number of items available for recovery, when it has been deleted, subject line and item type as well the original location

You can use the search fields to help you filtering the results; from the deletion period to the message ID (harder to know) or subject line or item type

Select the item(s) to recover and then click on the Recover deleted items button

When you hit the recover deleted items, this/these item(s) are recovered to the original folder and in the state it/they was/were when it was deleted (meaning unread/read…)