User Mailbox Size / quota Storage Consuming Concept

Muhammad Hussain 201 Reputation points

Dear Experts,

I want to confirm one thing if we create a new user mailbox with 1 GB quota so it consumes 1 GB storage instantly on Exchange disks? or it will utilize its storage on exchange disk day by day growth of mailbox?

In other words, it means a new mailbox assigned quota storage on disk would be thin or thick?
Please provide documentation as well if any available.

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Joyce Shen - MSFT 16,626 Reputation points

    Hi @Muhammad Hussain , agree with the replies above, the mailbox quota defines the maximum value of sending/receiving/warning for the mailbox, it doesn't reserve the space for the mailbox.

    Something more to clarify: from the database level, while adding data to Exchange mailboxes, the size of the Exchange database increases naturally. But, when it comes to deleting data, the size of the Exchange database may not reduce necessarily – it may remain the same.
    For example, let’s say that you remove 4GB of data from the 30GB Exchange database, so the expected size of the database should be 26GB. But, after removing the data, you will notice that the size remains the same, which is 30 GB. However, there would still be 4 GB space available to add new data. This ‘Available new mailbox size’ is commonly known as Whitespace.

    For the point above, referring to this link to get more information: How To Check Database White Space In Exchange

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  1. Ashok M 6,496 Reputation points


    Mailbox quota limit is the maximum limit for that mailbox which can be set on the mailbox or database level. Mailbox size consumption is on day-to-day basis. Exchange databases grow on a regular basis based on the number of mailboxes and the email sent/receive.

    For Exchange server storage, please refer

    Quota Limits

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  2. Andy David - MVP 137.9K Reputation points MVP

    In other words, it means a new mailbox assigned quota storage on disk would be thin or thick?


    In other words you are not allocating 1GB for each mailbox. You are saying that is the max. The max quota may never be reached by a mailbox.

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