Is there any way to have Mail automatically use our default "Sent" folder?

Question

We are a small college, with a fair number of users who use Macs and iOS devices, and we run an IMAP mail server. By default, our accounts are configured with Sent, Trash, Drafts, and Junk folders. Apple's Mail.app insists on "Sent Messages" and "Deleted Messages" rather than "Sent" and "Trash".
We instruct our users to use the menu command Mailbox > Use This Mailbox For > commands to select our server's folders on their desktops, and on iOS to use the Settings > Mail > Account > Advanced, but this is tedious and annoying. Most users get it about half right, so that some devices use our default "Sent", and some use "Sent Messages". (This happens with Trash as well, but most users are not concerned if their Trash differs device to device.)
Is there any server setting that can hint to Mail.app that it should use "Sent" rather than "Sent Messages"?
Apple has a support document about this issue, "Mountain Lion Mail: If messages aren't stored where expected on the server" (  http://support.apple.com/kb/PH11810 ).
However, that doc (and the similar one for Snow Leopard) merely says, "When Mail stores messages on the server, it looks for specific mailboxes, by name, in which to put the messages. If Mail doesn’t find those mailboxes on the server, it tries to create them on the server or, failing that, on your Mac."
The document does not specify what the "specific mailboxes" are, and certainly does not suggest that there is any way to have it cooperate better with our server, but perhaps there is a way?
(If I was trying to be a good IMAP client, I might look for any of "Sent", "Sent Messages", or "Sent Items", and use what I found before going to the next step of creating my own folder. Hard to imagine that any IMAP account would be initially configured without some "Sent" folder, so why not try to discover what the user has before pig-headly making your own.)

Answer 1

Unfortunately, I have not found a consise way to explain this to the general user, just a huge wall of text to work around something that Apple got wrong the first time they created an IMAP client, and has stubbornly persited with. Here's our documentation for this silly problem:
Special Folders on IMAP
The basic idea is that all IMAP mail programs keep all your mail on our server, so that, e.g. when you read or reply to a message, all of your devices can then show that message as read and replied to.
By convention, each IMAP program treats a few folders on the server as "Special", such as a "Trash" folder, that deleted messages get moved to, and a "Sent" folder, where each message you send gets copied. When they all pick the same special folders, all of your devices will show the same view of your mail. However, if different devices use different server folders for their "special" Sent folder, then the mail from these two devices will wind up in two different places, and be harder to find.
Unfortunately, Apple's Mail programs are particularly obscure and obtuse in the way they treat these folders: They show their special Sent and Trash folders on screen with the obvious names "Sent" and "Trash", but secretly, under the covers, they insist on using folders named, "Sent Messages" and "Deleted Messages" instead. Even if the server already has perfectly usable "Sent" and "Trash" folders, Apple clients will ignore them and create their own special case "special" folders.
If you only ever use Apple devices to look at your IMAP mail, you might never even notice their deception. But, if you sometimes use another mail client, such as webmail, you will encounter the confusing truth: When we created your account for the very first time, we add a "Sent" folder (actually named "Sent") and a Trash folder, named "Trash", and this is what everything except Apple's mail will use by default, because those folders are already their the first time the client connects to your account. However, even though Apple shows your special sent folder at the top of the list, with a paper-airplane icon, and labels it "Sent", in fact they ignore the existing "Sent" folder and make and use their own "Sent Messages."
SO, if you send some mail from webmail, it will be in your actual "Sent" folder, whereas if you send it from an Apple mail program, it will be put into your "Sent Messages" folder. If you look into either "Sent" special folder, you'll only find part of your previously sent mail.
Similarly for Trash, though most users find it more problematic to have two different Sent collections than to have multiple trash buckets.
To unify things, you can either set your non-Apple mail programs to use "Sent Messages" and "Deleted Items"; OR, you can set all of your Apple devices to use "Sent" and "Trash". Doesn't really matter which way you go, though if a majority of your devices are doing it a particular way, you should change the non-matching devices to agree with the majority.
(All clear so far? Why did Apple make this so hard? It would have been utterly simple for them to check for an existing "Sent" folder, and to use one if there is one, rather than to always stubbornly create and use a new "Sent Messages" folder. Then, they add to the problem by pretending that their new "Sent Messages" folder is really just named "Sent". Stupidity all the way down.)
Anyways, to find out what the majority of your devices are doing, check them each to see which of the "sent" folders shows up in the "normal" list of folders rather than in the "special" location, that is, what folder name is in the list at the bottom of the folder area, rather than up at the special "Sent" icon, (because the special one will always be labeled "Sent", not matter what the actual folder name is).
For example, say that on all-but-one of your mail setups, you see a "Sent Messages" folder down in the normal list, and on the other device, you see "Sent" down in the normal list.
In that case, you'd want to set the "different" device to make the folder named "Sent" be the special one, instead of the "Sent Messages" that it was currently using.
Conversely, if all but one showed "Sent" down in the regular folder area, and only one showed "Sent Messages", then you'd want to make "Sent Messages" the special folder on the odd device.
Once you have decided, see the specific sections below for the procedure to set the "special" folders for Apple's Mail.app on a Mac, Apple's Mail on an iPhone/Pad/Pod, or for RoundCube webmail, or for Thunderbird.
Once you have every device using the same sent folder, then you can move any messages from the "extra" version of the folder into your special folder, and then you can delete the extra folder. (If you delete this extra folder and it later re-appears, then it means one of your mail programs is still using it as its "special" folder, and recreating it.)
Similarly for Trash, though probably you could delete the extra trash folder without moving the files, because they are trash.
Here are the details for changing the Special Mail Folders on the systems we use:
A) iPhone, iPad, iPod:
As a first step, use Settings > Mail to set your device to read your email account, then open the Mail program so that it will read the list of all of your folders from the mail server. After that, go back to Settings > Mail to make sure it is using the desired special mailboxes on the server.
Select your IMAP account in the settings tool, and then press the button for "Advanced" settings, and find the list of special mailboxes, e.g. Sent, Trash, Drafts. For each, scroll through the list of folders on the server to choose the folder you wish to use for that function.
Note: iPhones/Pads/Pods also can be set to keep sent mail locally on the device. This is a spectacularly stupid choice for normal IMAP, as none of your other devices will be able to see the messages you send from your phone.
B) Mail.app on Mac desktops and laptops:
Set up mail so that it reads your messages and folders from the mail server.
Select the "Sent" folder that you wish to use in the list of folders at the lower left of the mail window. (On newer Macs, the folders may be hidden by default. Use the "View > Show Folder List" menu command to display them if necessary.)
Use the menu command "Mailbox > Use This Mailbox For > Sent" to specify that the selected mail box is the special folder for sent mail, and similarly for your Trash, Junk, or Drafts folders.
C) RoundCube Webmail (with the standard skin):
Login to your webmail site , and select the "Settings" icon in the upper right of the window, which has a "Gear" icon. This will display a "Settings" panel with buttons for "Preferences", "Folders", and "Identities" settings. When you first open the Settings panel, the "Section" panel shows a row of buttons for different Preferences.
Click "Special Folders" in the "Section" list to open a list of "Drafts", "Sent", "Junk", and "Trash". Each special folder is followed by a menu of all your server folders. Select the server folder to use for each special folder.
D): Thunderbird:
After you have set up your connection to your IMAP account, click "Get Mail" to fetch your existing mail and list of folders on the server.
Next, select the menu command "Options > Account Settings…" (Note that on current versions of Thunderbird, the default menu drops down from an icon of three horizontal bars, in the upper right corner of the mail window. You can use the Options command in this menu to display a menu bar at the top of the Thunderbird window if you wish. With the full menu, the menu command to access the special folders settings is "Tools > Account Settings…"
Select "Copies and Folders" in the list at the left of the Account Settings window. This panel has a section for Sent mail, Archives, Drafts, and Templates. Select "Junk Settings" in the list at left to specify the location of the Junk special folder.
For each special folder, the default choice is the the folder on the server with the "typical" name, e.g. "Sent" for sent, and "Trash" for trash. To use a different name, select the "Other:" option for the folder, and then choose the desired folder from the list of folders on the server.
Oof! That's a lot of explaining for a issue that Apple should have gotten right in the first place, or at least should have fixed in their next several tries. It would not break any existing functionality if they merely used whatever folder the server had created, and only made their own if there was none.