The email address can be shared in Office 365 so that the same person can handle two email addresses. And, they can send a reply as well from the single login. For e.g. if there is email address info@<your domain> and account@<your domain> the info@<your domain> can be shared with account@<your domain>
To share the mailbox, please follow the procedure as described below:
First go to the Microsoft office 365 login page and login using your login details. After successfully login go to admin area of the Office 365, where you can find the menu as “SHARED MAILBOX”
Once you do this click + button to add new mailbox which you want to share. Please fill the required fields and save it.To make sure it is working fine and all the settings has been entered correctly, select the mailbox by selecting the checkbox options and you can see the Edit more properties (preview the image below).
Now, try to login to your mailbox using your login details. Once you are logged in you need to add your shared mailbox, just right click and add Shared Mailbox. You can see your mailbox folder displayed there just under your main account.
Try sending an email from shared mailbox. Compose new email, and select ..(option which is at last) and click Show From. Your mail address is displayed on From field. Just delete your mail email address from that From field and type in your shared mailbox email address. And, you can send an email.
All the incoming email on info@<your domain> are received on your shared mail inbox folder.