Deleted items when using IMAP

Why the messages you delete stay in your mailbox until you purge them.

IMAP keeps your mail on the server so that every device sees the same mailbox. Deleting a message does not remove it straight away. The server marks the message as deleted, and your mail program either shows it with a line through it or hides it from the folder.

Until you purge the folder, those messages still count towards the size of your mailbox.

Purging a folder

Every mail program words this differently. Look for Purge, Expunge, Compact or Empty Trash, usually on the Edit or Folder menu, then apply it to the folder you want to clear. The server removes the marked messages permanently.

Most programs can also purge on their own, either when you leave a folder or when you close the program. If your mailbox fills up faster than you expect, check that setting first.

Programs that use a Trash folder

Some programs move deleted messages into a Trash or Deleted Items folder instead of marking them where they sit. That folder is on the server as well, so emptying it is what frees the space.