The visible folders that you see in Thunderbird are controlled by 'subscriptions'.

You can enable or disable the subscription feature. If it is disabled, you will see all folders, including normally-hidden system folders.

You can enable or disable the subscription feature within Thunderbird by clicking on:

Tools → Account Settings → Server Settings → Advanced → Show Only Subscribed Folders

Once the subscription feature is enabled, you can manage the 'visible' or subscribed folders by clicking on:

File → Subscribe

from within Thunderbird. Select all IMAP folders that you want to be visible.

Deleting messages with an IMAP mail client is a little different than deleting messages in a POP mail client. Most POP mail clients will actually move deleted messages into another mail folder. While this is convenient and fast with a local mail store located on your own PC, it is another matter with a server-based message store.

To change how deleted mail is handled, go to:

Tools → Account Settings → Server Settings → When I delete a message

• By default it is set to “Move it to the Trash Folder”.
• If “Remove it Immediately” is set, the message will not go to the Trash folder.
• If “Mark it as deleted” is set, deleted messages show a line through the text and a red “X” icon.

If you have a very large mail store, or if your server is older or slower or if you just like speed, you may opt to choose 'mark as deleted'.

• This is very fast and efficient as it simply changes an attribute of the message, rather than physically moving it.
• Messages will then display with a line through them showing them as deleted.
• Messages marked as deleted can be undeleted too.
• You can choose not to display messages marked as deleted so they don't 'clutter' the display.
• Messages are truly deleted with an 'expunge' operation
  • Messages marked as deleted are expunged when you Compact Folders.
  • You can also set Clean up (“Expunge”) Inbox on Exit
    • If set, messages get physically deleted when you exit from Thunderbird.

If you like to keep your deleted mail for a while and you have the disk space, you can use the (default) “Move it to the Trash Folder” option.

• This option uses more disk space.
• This option is slower by far than 'Mark as Deleted'.
• This may be more like what you were used to with other mail clients.
• You can specify the folder where deleted messages are stored.
  • If you use a 'local folder', deleted items will not be visible from other IMAP clients you might use such as webmail.
  • An IMAP folder is more universally visible, but uses up your disk quota if you have one.
  • You may need to coordinate (adjust) all of your IMAP clients to use the same Trash folder
    • Different IMAP mail clients default to using different folder names

Other folders that might need adjustments if you use more than one IMAP client might include:

• Sent Mail
• Drafts
• Templates
• Archives

Most users will make use of at least Sent and Drafts.

To adjust the folders into which these items are stored:

Tools → Account Settings → Copies & Folders