Exchange Server applies a mailbox size limit to all Mailbox Databases by default in Exchange 2007 and newer editions. By association, all mailboxes use the limit settings of the database they're on unless Exchange administrators specify otherwise. Administrators can also configure additional mailbox limits and exceptions to be applied either at the database or the individual mailbox level.
If end users are approaching their mailboxes' limits they'll receive a notice in Outlook. The IssueWarningQuota property of a database or mailbox, which is set to 1.9 GB by default, triggers the message. If a user doesn't remove items from the mailbox, she'll continue to receive warning messages until the ProhibitSendQuota setting prevents her from sending any further messages. If she takes no other action, she could eventually reach the ProhibitSendReceiveQuota setting, which is the actual hard limit.
For many years, Exchange administrators encouraged people in their organizations to use the automatic archiving feature of Outlook, AutoArchive. A main reason to use AutoArchive is to move any mail older than an age the end user has defined off of the Exchange Server; it then stores a local copy of the mail in a PST file on the end users' local machines. While this may be desirable if you're looking to minimizing the cost of storage on Exchange Servers, many organizations actually discourage this behavior because of compliance purposes. In fact, Outlook 2010 and newer editions disable AutoArchive by default. As an alternative to AutoArchive and PST usage, Exchange 2013 provides the In-Place Archiving feature. There are also a number of third-party archive options for Exchange organizations, including Barracuda Email Archiver, Netmail Archive and Symantec Enterprise Vault. Organizations that implement these options allow their end users to retain email items long term without exceeding mailbox limits. Most importantly, this reduces an organization's potential exposure to compliance breaches.
About the author:
Richard Luckett is a consultant and instructor specializing in messaging and unified communications. He's been a certified professional with Microsoft since 1996 and has 20 years of experience in the public and private sectors. Luckett is a Microsoft Certified Trainer with more than 15 years of training experience with the Microsoft product line and received the Exchange MVP award in 2006, 2007 and 2008. He's also an expert in deploying and integrating Exchange Server and Lync Server. He leads the Microsoft training and consulting practice at LITSG.
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