Mailbox Size Limitations - Best Practices

Oh, and another thing is to consider what types of email your users receive.  If users get faxes, voice mails, graphics, pictures, etc., all in their mailbox, they will need a lot more space for a reasonable amount of storage than if they receive and send mostly simple text mails.  This goes along with dariusg's comments about different users having different limits.  We adjust the limits for user taking into account the types of emails they are likely to receive as well as their status in the company.  We even sometimes take into account how loudly the user is likely to complain if they get warning messages and have to purge emails.  

Thank you all for your responses and feedback. So focusing purely on responsiveness of the system, the factors impacting Exchange performance are:

Hardware (CPU, Memory, Disk  (speed+capacity) firmware versions
Usage (aggregate of users sending/receiving/deleting, etc + other apps: AV, BES + backups + other management software or apps pulling from/pushing to Exchange)
Store Size
Mailbox Size
# of messages
State of the store (frag'd/defrag'd)

I may have missed some, but again from a pure performance standpoint, is there a point at which the size of a mailbox begins to adversely impact the end-user experience (i.e. "my email is slow"). I read about the 5000 message per folder recommendation. What about aggregate size per mailbox and best practices. If 5000k messages per folder = bad, what else = bad or optimal for that manner with regard to mailbox size? This would be both from the standpoint of the Outlook 2003 or 2007 clients as well as the Exchange server.

What they say is that PST files are to become problems once they are at 2 GB and over but I have some emails at the office that are around 3 GB which don't give me any problems except they run a little slower but that is expected with anything that is 3 GB in size. Right now I have 9,000 messages in my mailbox with a size of 682 MB but my Marketing Dir. has 3,000 messages with a mailbox size of 1.95 GB. Again going by email messages isn't the way to go because of another factor attachments on email.

I have had users with maiboxes on my mailservers close to 3GB without any issues...yes it hinders your backup processes, yes it will slowdown a recovery in a diaster...and yes he is potentially taking up about 10GB of allocated space all around...so that is where you have to put the policy down and implement and enforce...you will not be able to follow all the best practices for Exchange or make a perfect enviroment for exchange unless you are a huge IT department with lots of money...like say Microsoft...LOL...but you can do everything within your power to get close and policy is a big one...

If you are really considering best practices I would start of with the Best Practice Analyzer you can get it here... http://www.microsoft.com/downloads/details.aspx?familyid=DBAB201F-4BEE-4943-AC22-E2DDBD258DF3&displaylang=en

Then get a good Exchange Server Book and read it maybe read it twice...and then go from there...

Look at you network what does your backbone look like, 100 Mb between servers, consider gigabit.
What type of storage are you using on your Exchange server, internal 7200 rpm drives, and are your storage databases on the same RAID container and partition as your transaction logs?

There is a lot to Exchange to follow the Best Practices...you have to just evaluate your environment and do the best that you can...and make sure you have a good Disaster Recovery Plan.

Thanks again for your feedback. The Best Practices Analyzer is for existing Exchange servers and as we're in the process of building our first, this will not yield much useful info. As for reading Exchange books, I've read a handful and have scoured the internet, but have been unable to find any line in the sand that says "mailbox > X GB = bad". I understand the challenges huge stores bring to DR, but the audience I need to present to is a group of execs who want to know the bottom line in terms of performance, industry-leading publications research recommendations (Gartner/Forrester) and what this will mean to them as the end user. As soon as I start talking about DR, bandwidth, or RAID, eyes will glaze over and I might as well go home. Sorry for not being clearer in my request and thanks again for your help!

I think when presenting to users, you need to also take into consideration what kind of archiving you are going to do.  I work with law firms mostly, and believe me, they HATE to delete information, so they end up with huge archive files (usually in the form of .PSTs - don't ask!).  So, you might want to think about what type(s) of archiving you want to use and the impact of that on the size limits of people's mailboxes.  You can present to your execs as a total solution, i.e., we are going to limit your mailbox size to 1GB (or whatever) for performance reasons, but we are also going to implement an archiving solution so that when you delete items from your mailbox, they will still be recoverable from our archive if necessary.  This might make them feel more comfortable with the limits you need to impose.

Also, I wanted to respond to your question about performance vs. the size of the mailbox.  Unfortunately, there's no one "final answer" that will get you that $1 million.  In my experience, it really depends on the size of the individual messages more than the aggregate size of the mailbox.  A mailbox with 5000 messages, each of 1K or less in size, will not be that slow, except perhaps when you open it for the first time, due to the fact that Outlook has to build the views and index the contents of the mailbox. However, a mailbox with 5000 messages, each 1MB in size would be much slower.  Also, opening individual messages that are very large (i.e., something with a 10MB attachment) can be very slow, even if the mailbox only has 50 messages in it. So, again IMO, you need to take into account the average size of the individual messages when you weigh performance against other factors.

We do a archiving scheme which has worked pretty well. We have each PST file that are archived listed with a year then the user would pull over the emails that are needed to be archived into the correct archive file which is then sent to the server for backup.

Thank you for your help and feedback!

Just as an additional comment, in terms of archiving solutions we use Symantec Enterprise Vault and it does the job tremendously well.  Since email is archived every night and deleted from the mail server(although you can customize all of that) leaving behind only a 'stub' of the original message in users' mailboxes (which can be double-clicked to open the original message from the archive, meaning it's seamless to the user) mailbox sizes don't need to be very big at all.  Ours are still set at 50MB and unless a user receives a particularly large attachment in one message during the day this doesn't present any problems for us at all.  

The mail store is tiny in relative terms and the messages on the archive server are compressed to a fraction of their original size, as well as being sorted so that only one copy of each message exists on the server regardless of how many people in the organization have it in the mailboxes.

I disagree with this comment: "Now, it's possible to use space on another drive, but it's a lot easier if you have that free space on the same drive as your database(s)."
Talking about using eseutil; you will get much better performance if the temp location for files that eseutil uses is on a seperate physical disk (or raid group). Otherwise eseutil will hammer the same disk the database is on and store the temp files on the same disk and it will take exponentially longer to perform this task (as apposed to having the temp files on another physcial disk).
Yes it is easier to have more free space on one disk but when it takes twice as long to perform the same operation, is that really easier?