To add storage/disk space to any of your Open-Xchange mailboxes, please follow the instructions below:
1. Log in to SiteControl and click the Setup and Manage Email link available on the home page.
Alternatively, you can click on the Email icon under Manage Services, which will open the email section of SiteControl. On the new page, you can select Open-Xchange App Suite.
2. Select the proper domain name from the Currently Managing drop-down menu.
3. From the Email Addresses list, locate the mailbox you wish to increase the storage for and click on Edit.
4. Locate the Mailbox Storage Space section and click on Update.
5. In the newly displayed box with the current size of the mailbox, enter a desired value (in GB) you wish your mailbox to have in total and click Update Quota.
Important: There is a limit on increasing the quota with 50GB per single update!
6. Upon successful storage upgrade, a confirmation message will appear on the top of the page as well as a green checkbox against the Mailbox Storage Space title.
7. Finally, you can verify the new quota at the Email Addresses list by clicking on Cancel and Go back, which would lead you back to the Open-Xchange App Suite overview page.