To keep team- or project-related email organized, you can add a site mailbox to a SharePoint site. People simply send email to the site mailbox email address. Then, team members who have the correct permissions can view, organize, and respond to email from the site mailbox in SharePoint by using the same tools they’re familiar with from Outlook on the web.
Important:The site mailbox feature in SharePoint is being deprecated beginning in March, 2017. This feature will be removed entirely in a future release. New SharePoint organizations no longer have access to the site mailbox feature. Existing SharePoint organizations can no longer create new site mailboxes. Any site mailbox that was set up and deployed before March, 2017 will continue to function.
We will provide a process to help transition your existing site mailbox sites to aMicrosoft 365 Group in September, 2017. If you currently use the site mailbox feature in SharePoint, you should consider changing to Microsoft 365 Groups instead to support your email collaborative scenarios. For more information, see Use Microsoft 365 Groups instead of Site Mailboxes.
Note:The site mailbox feature will remain supported, but deprecated in SharePoint Server 2019, SharePoint Server 2016, SharePoint 2013 and SharePoint 2010 products. Customers are recommended to explore shared mailboxes as an alternative to site mailboxes.
You can:
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Add a site mailbox (You must be a site owner to do this.)
Anyone can send email to the site mailbox email address.
Here are the criteria to read, organize, respond to, or delete messages in a site mailbox:
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Each person must have a license for both SharePoint and Exchange in the same Microsoft 365 subscription.
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Each person must be either in the default members group or in the default owners group for the site, or have Contribute permissions. When you set up the site, make sure you give access to team members who need it.
Note:External team members cannot use site mailboxes.
If you decide you don’t want a site mailbox after you’ve created one, you can prevent the site mailbox from showing up on the site.
Frequently asked questions about managing site mailboxes
Here are answers to common questions that might come up as you start using site mailboxes in your organization.
Questions about using site mailboxes
How can a site member find out who can see the site mailbox?
In Outlook on the web, at the top-right corner, click Settings 
What happens if two people simultaneously edit a draft email in the site mailbox by using the SharePoint site’s Site Mailbox app?
The second person’s edits overwrite the first person’s changes.
Questions about creating and removing site mailboxes
Do I need to assign a license to the site mailbox email address?
No. The site email address does not require an Exchange license.
Are there situations when I shouldn’t use a site mailbox?
There are times when a site mailbox may not be appropriate:
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Consider confidentiality—any email in a site mailbox can be read or forwarded by any site member.
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Because the site mailbox is a shared workspace, any site mailbox user can rearrange and delete email.
Can I rename a site mailbox?
The display name of a site mailbox is the SharePoint team site display name. If you change the display name of the site in SharePoint, the display name also changes in Outlook. However, the site email address won’t be changed.
Can I change a site mailbox email address?
No. The email address for a site can’t be changed after it’s created. The email address is generated from the display name for the site when the site mailbox was created.
If the site display name uses characters from a non-English alphabet or has three or fewer characters from the English alphabet, the display name isn’t used for the email address. Instead, to ensure that the email address is valid, the email address is automatically generated. These email addresses begin with a prefix of SM, followed by the two-digit year, the three-digit day of the year, and four random letters.
