Folders and synchronisation: why you have "Sent" twice

Module 3: Managing your mailbox · Reading time: 9 minutes

Learning objective: After this lesson, you can explain how IMAP folders work on the server, make sure your mail program uses the correct special folders, and prevent mail from being duplicated or lost.

Key concepts: IMAP folder, folder list on the server, special folders (Sent, Trash, Drafts, Spam, Archive), special-use (RFC 6154), folder mapping, subscribing to folders, deleting and permanently deleting (expunge), synchronisation period, offline copy

Where are your folders actually stored?

In lesson 1.3 you saw the difference between IMAP and POP3. With IMAP, your mail is stored on the server, and your mail program shows what's there. This also applies to folders. If you create a folder called "Quotes" in Thunderbird, Thunderbird creates that folder on the server. Your phone will then see it too, and so will webmail.

That's exactly what you want. But it also means a mail program can create folders on the server that you didn't intend. And if two programs disagree about what a folder is called, you end up with two of them.

A few things to know about folders on an IMAP server:

• The Inbox is always called INBOX on the server. That's the only folder with a fixed name. Your program translates it to "Inbox", "Postvak IN" or similar.
• All other folders have a free name. The server doesn't recognise a "real" Sent folder unless it explicitly says so (see below).
• Subfolders are separated by a character, usually a dot or a forward slash: INBOX.Offertes or Offertes/2026. You rarely see this, but it explains why some programs show all folders nested under the Inbox.
• A program sometimes only shows the folders it's subscribed to. A folder that does exist on the server but that you're not subscribed to then appears to have disappeared.

The problem with special folders

Your mail program needs a few folders to work properly:

Each program has its own preference. Apple Mail uses different names by default than Outlook, and Outlook different names again than the Gmail app. If you set up your mailbox on three devices without paying attention, this can happen:

• Outlook puts sent mail in Sent Items.
• Your iPhone puts sent mail in Sent Messages.
• Webmail puts sent mail in Sent.

Then you end up with three Sent folders, and on each device you only see part of what you've sent. That's the most common complaint about IMAP: "I don't see on my phone what I sent from my computer".

The solution: special-use

Since 2011 there's been an extension to IMAP that lets the server indicate which folder is for what: special-use (RFC 6154). The server then says, for example, "this folder is called Sent and has the function \Sent". A modern mail program picks that up and no longer creates its own folder.

Most mail servers support this, and so do most programs. But things still often go wrong with:

• a mailbox that's existed for years, in which older programs have already created their own folders;
• a mailbox that's been moved from another provider, where the folders were named differently;
• programs you set up manually before the server offered special-use;
• POP3 (there are no folders on the server there, so each device keeps its own Sent folder locally).

Mapping the folders correctly yourself

Already have duplicate folders, or not sure? Then choose one folder per function and tell each program which folder that is. Preferably choose the folder the server itself designates. You can recognise it in webmail: the Sent folder usually appears at the top with its own icon.

Where do you set this up?

• Thunderbird: Account Settings, your account, Copies & Folders (Sent, Drafts, Archive) and Server Settings (what happens to deleted messages, and to which folder).
• Apple Mail on the Mac: Settings, Accounts, your account, Mailbox Behaviours. On the iPhone: Settings, Mail, Accounts, your account, the account itself, Advanced, and then choose the server folder per function.
• Classic Outlook: for an IMAP account, you choose the path of the main folder and the folder for deleted items in the account settings (More Settings, Advanced). For sent items, classic Outlook has no choice in many versions: it uses the folder the server designates, and otherwise its own.
• Gmail app: works with the folder the server designates; you can't configure it per folder.

Afterwards, move the mail from the redundant folders to the chosen folder, and delete the empty folders. Do this on one device (preferably webmail or the computer) and wait for the other devices to pick it up.

Deleting works in two steps

With IMAP, deleting is really just setting a flag. A message gets the deleted marker (\Deleted), but still remains on the server. Only when the program issues the expunge command is it actually gone. Most programs work like this:

1. You press Delete. The program moves the message to Trash (actually: it copies it to Trash and marks the original as deleted).
2. The original is permanently deleted (expunged) either immediately or when you exit.
3. Only when you empty the Trash is the message gone from the server.

Some programs are configured differently. Then you see messages with a line through them that just won't go away: they're marked, but never permanently deleted. And they still count towards your storage. In that case, look in your program for Compact Folder (Thunderbird), Erase Deleted Messages, or a setting such as "permanently remove deleted items when leaving the folder".

Important: deleting on one device means deleting on all devices. That's the whole point of IMAP. If you want a message gone from your phone but kept on your computer, that's not possible with IMAP. The most you can do is synchronise a shorter period on the phone (see below).

Is something missing anyway? Many providers keep backups from which a mailbox or folder can be restored, but usually only for a limited period. Don't rely on that as an archive.

How much do you synchronise?

A mail program doesn't need to download everything. On the phone, it's often handy to synchronise only the last few weeks, or to only push the Inbox. That saves space and battery. It changes nothing on the server: the old mail is still there, you just don't see it on that device.

On the computer, most programs create an offline copy of the mailbox (Outlook in a .ost file, Thunderbird and Apple Mail in their own folder). That's a copy, not a backup: if you delete something on the server, it also disappears from the offline copy. A genuine local storage location is a folder you create yourself under Local Folders (Thunderbird), On My Mac (Apple Mail), or in a .pst data file (Outlook). Whatever you drag there is no longer on the server. More on this in lesson 3.2.

In practice: what it looks like in a panel

In WebOké's webmail (Roundcube), you see all the server's folders on the left. Under Settings, Folders, you can create, rename and delete folders, and subscribe or unsubscribe. Under Settings, Preferences, Special Folders, you can see which folder is used as Sent, Drafts, Trash and Spam. Other providers work similarly; their webmail might be called something else, but almost every webmail has this kind of folder management.

Summary

• With IMAP, your folders are stored on the server too. Every device sees the same folders.
• Only INBOX has a fixed name. Sent, Trash, Drafts and Spam are named differently per program, unless the server designates them (special-use, RFC 6154).
• You fix duplicate Sent folders by choosing one folder per function and pointing every program to it.
• Deleting in IMAP is marking, followed by permanently erasing (expunge). Marked messages still count towards your storage.
• An offline copy is not a backup; a local folder is a genuinely separate storage location.

Quiz

Exercise

Exercise O3.1: Checking your folders. Open your mailbox in webmail and on every device where you use it. Note down, per device, which folder it uses for Sent, Trash, Drafts and Spam. Do you have duplicate folders? Choose one per function, point every device to it, move the mail across, and delete the empty folders. Then fill in the checklist and answer the question: which folder did the server itself designate, and how did you recognise it?

Further reading

The steps in these articles apply to WebOké's panels; with other providers it works similarly.

• DirectAdmin guide 8.7: IMAP or POP3: what's the difference?
• What is IMAP or POP3 and how does it work?
• How do I delete a message in IMAP?
• DirectAdmin guide 18.11: An e-mail was accidentally deleted
• Restore mailbox or deleted emails from the backup
• RFC 6154 (IMAP LIST Extension for Special-Use Mailboxes)