Increase Mailbox quota Size at Database Level in Exchange Server 2013 /2016 There can be many reasons due to which you need to set Mailbox quota in Exchange 2013/2016 for all Users at database level. And you can do this just by following below simple steps: 1. Start ECP, open https://mailserveraddress/ecp from browser then Click on Servers >> Database tab. and select the database that you want to work on it. Mailbox DB selection on exchange 2. Select the database of which you want to change the size. Mailbox DB properties 3. Click on limits and set the required size for Database. Note: Size limit will be applicable for all the mailboxes that are included in that Database.