Shared mailboxes in Office 365 make it easy for a group of people to monitor and send email from a common email addresses. Example for such usage is a support mailbox, where customers can send an email to, and open a support request.

What makes Office365 shared mailbox so attractive is the fact that it is free of charge.
The shared mailbox itself does not require any license, only the members who have permission to send and receive as the shared mailbox requires a valid (active) office 365 license.

However, while it is very easy to setup a shared mailbox, overlooking the members, and their settings may result an SMTP error messages during mail submissions. One common error is:

SMTP Error: data not accepted.SMTP server error: DATA END command failed Detail: 5.7.60 SMTP; Client does not have permissions to send as this sender SMTP code: 550

A quick walk through – Creating an Office365 shared mailbox

Each step is backed up by an image, If you haven’t done so already, follow these steps to create one.

  1. At the Office365 Admin Center home, type “Shared” at the task search box, the click “Add shared mailbox”.
  2. Enter the display name and the email address for the shared mailbox, then click “Add”.
  3. With the “Shared mailbox was created” confirmation message shown, click on “Add members to mailbox”.
  4. Add members as needed. Do not forget to click on the “+” sign to actually add user membership. When all members are added click save.
  5. The shared mailbox properties window is now shown. The shared mailbox is configured.


In a perfect world that should have been enough for the members to send email from the shared mailbox, unfortunately if you will try to do it right now, you will most likely end with an SMTP data error of some kind.

Use arrows to browse slides. Click on image to enlarge.

Luckily, the solution to the problem is an easy one. It is a commonly overlooked setting called “Send on behalf”, also known as “Send as” that is not being added automatically when you add a member to a shared mailbox.

Manually granting “Send on behalf” right will most likely fix the “SMTP Error: data not accepted….SMTP; Client does not have permissions to send as this sender SMTP code: 550” error message.

At the shared mailbox properties page, click on “Customize permissions”, and grant “Send on behalf” permission to the relevant user(s).


As always, You ‘re welcome to share your comments and experience using the comments below.
Good luck.

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