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theorical and practical limit of mailboxes on single server

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  • theorical and practical limit of mailboxes on single server

    Hi everyone
    I was wondering about the theorical and practical number of mailboxes on a single exchange enterprise server.
    I have seen some business cases with 5000 mboxes on a single server (300 GB total of storage), but also I sometimes see microsoft recommend up to 1500 mboxes.

    Is there anyone who can explain why this limit?
    Is there also anyone who can tell me if he/she knows any Businesses with more than 5000 mailboxes on a single server?


  • #2
    All our student mailboxes are on one server (thats 3000ish). But they are infrequent users compared to business users. One access every couple of days on average. Some never log in! Plus they have 20mb max size so the current database size is 14gb - just to give you an idea.
    Server 2000 MCP
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    • #3
      Planning server capacity is something that needs to be taken into account prior to designing the network, AD and Exchange plans. There are many whitepapers available on Microsoft's website, plus various blogs and articles written by other experts. A tool called AD Sizer can also help in some areas.

      Basically, the stronger the hardware the more you can load on the server. I've seen servers with 3000 mailboxes and stores as large as Tera Bytes built on strong hardware and expensive storage devices. On the other hand, a poor-man's PC-server-wanna-be with 2 IDE disks will only hold as much as it can. I use a 2X2 rule + 5 disks for servers running 500-1500 mailboxes, and if they cause a lot of workload I will naturally go for better storage systems.

      Sometimes you'll be better off with 2 mid-range servers running at 35% than a super high-range server running at 10%.

      Daniel Petri
      Microsoft Most Valuable Professional - Active Directory Directory Services


      • #4
        Hi Daniel
        My question was a bit different. I'm not talking about sizing a server or the number of mailboxes depending for hardware; my question is: why microsoft recommends up to 1500 mboxes regardless hardware.
        Let's suppose we can build a server with TBs and TBs of storage, a certain number of CPU, and a certain GB of RAM: which is the limit point of Exchange server regarding the number of mailboxes? does it just depend by hardware limit or does it depend by microsoft architechture limits?
        I hope I have explained this concept as well