Does your iPhone sync with your law firm's e-mail server? Does your law firm (like most) use Microsoft Exchange? If so, you might notice that your iPhone only keeps the last three days of e-mail on the iPhone. That is the default setting when you set up your iPhone to work with an Exchange mail account.
But you can change this default setting. Go to Settings --> Mail, Contacts, Calendars. On the top portion of the next screen you will see your "Accounts" listed. Tap on the entry for your Exchange e-mail. Then on the bottom of the next screen, tap on the setting "Mail days to sync." Your choices are 1 Day, 3 Days (the default), 1 Week, 2 Weeks, 1 Month or No Limit. Simply select "No Limit" and you will have unlimited e-mail. Every e-mail that you see in Outlook will also sync to your iPhone.
You may notice at the bottom of the "Mail, Contacts, Calendars" screen that there is a setting under "Mail" called "Show" that allows you to show from 25 to 200 recent messages. You might think that this means that you can only see up to your last 200 messages on your iPhone, but for Exchange mail accounts, this option is ignored. This is a little confusing and it seems that Apple should tell you this -- and they do if you know where to look; here is an Apple Knowledge Base article on the subject. Thus, no matter what your "Show" setting, you will see anywhere from 1 day to 1 month to unlimited Exchange messages, depending upon what you set as your "Mail days to sync."
Of course, the amount of e-mail you can store on your iPhone is subject to how much free space you have on your iPhone. But many companies already impose a limit on the amount of e-mail you can store on your Exchange server. At my firm, that limit is 500 MB, and I consider it worthwhile to devote up to one-half of one of the 16 GBs on my iPhone 3G to e-mail.
Scrolling back through thousands of messages can take a little time, but it is nice to know that the e-mails are there if you need them. I wish that the Mail and Calendar apps gave you an option to jump to a specific date, and I also wish that you could search for a specific e-mail or search for a specific calendar entry -- two features that would make it much easier to manage a large number of e-mails or calendar entries on the iPhone. Hopefully this will be added in a future software update.
Thanks to my law partner Louis Lacour for mentioning the "Mail days to sync" option to me.