Add a mailbox to the contentstore subclient.
In the navigation pane, expand Solutions >Apps, and then click the Exchange Apps.
In the Email Journaling area, click on the App, on the upper-right corner,click Add App, select the mailboxes from the mailboxes list, and then click Add Mailbox.
The Create ContentStore mailbox dialog box appears.
In the Display name box, type the mailbox name.
In the SMTP address box, type the name of the email address of the mail contact.
For example, firstname.lastname@example.org.
From the Exchange plan list, select a journal mailbox plan.
In the Certificate file, browse to the SSL certificate and upload it to the ContentStore Mail Server (SMTP).
The certificate must include the fully qualified domain names of the endpoints to which the SMTP clients connect. Usually, this is the SMTP host name.
The supported format is PKCS#12 (.p12 or .pfx) and it must contain both public key certificates and private keys.
Important: If you use Office 365 with Exchange (Exchange Online), after you upload the SSL certificate and enable TLS for SMTP, you must enable TLS on the Send connector. For more information, see the Microsoft TechNet article: "Set up connectors for secure mail flow with a partner organization": https://technet.microsoft.com/en-us/library/dn751021(v=exchg.150).aspx.
In the Password, enter the SSL certificate password.
From the ContentStore mail server list, select the clients where the ContentStore Mail Server (SMTP) is installed.
In the Cache location, browse to the ContentStore Mail Server (SMTP) folder.