As páginas do Google Supprt dizem:
- Do NOT save deleted messages on the server. Messages that are deleted from an IMAP folder (except for those in [Gmail]/Spam or [Gmail]/Trash) only have that label removed and still exist in All Mail. Hence, your client doesn't need to store an extra copy of a deleted message.
- Do NOT save deleted messages to your [Gmail]/Trash folder because this will delete a message in all folders.
Além disso:
If you delete a message from your inbox or one of your custom folders in your IMAP1 client, it will still appear in [Gmail]/All Mail.
Here's why: in most folders, deleting a message simply removes that folder's label from the message, including the label identifying the message as being in your inbox. [Gmail]/All Mail shows all of your messages, whether or not they have labels attached to them. If you want to delete a message from all folders, move it to the [Gmail]/Trash folder.
If you delete a message from [Gmail]/Spam or [Gmail]/Trash, it will be deleted permanently.
Nancy McGough, com tinta infinita, resume o comportamento não padrão do Gmail da seguinte forma:
- To put a message in multiple folders, use Pine's Save (S) command multiple times. Be careful about whether you copy or move the message. Pine's Save ^R subcommand is a toggle that controls whether or not the message is Removed from the current folder after the Save is done.
- When you use Pine to "Delete" (D) a non-spam non-trash message, the Gmail IMAP server immediately deletes & expunges the message from the current folder, but it will still be in the [Gmail]/All Mail special folder and any other folders that it happens to be in.
- To "archive" a message that is in your Gmail INBOX, use the Pine D command to Delete it from the INBOX. It will still be archived in [Gmail]/All Mail. Tip: When accesssing your Gmail INBOX with Pine, you can think of D as meaning Done (but don't think this way in non-Gmail folders!).
- When you use Pine to "Delete" (D) a message in the [Gmail]/All Mail special folder, the command is ignored.
- To delete a message from all the folders it is in, including the special [Gmail]/All Mail folder, use Pine's Save (S) command to move or copy the message to the [Gmail]/Trash special folder.
- When you use Pine to "Delete" (D) a message in either the [Gmail]/Trash or the [Gmail]/Spam special folder, the message is immediately deleted & expunged and cannot be recovered.
- To search all your non-spam non-trash Gmail messages, open the [Gmail]/All Mail folder and use Pine's Select (;) command and other aggregate operations to zoom (Z) in on the search results.
- Pine folder means Gmail label!
Fonte: link
Não inclua o "comportamento estranho" ao qual você está vinculado. Só posso recomendar experimentando cautelosamente com a exclusão na pasta [Gmail] / Lixeira ou, de forma mais pragmática, se você for usar o serviço deles e tentar adotar a filosofia do google de excluir e-mails: ou seja, não faça isso e não faça preocupe-se com os e-mails excluídos encontrados no [Gmail] / Todos os e-mails porque o espaço em disco é barato.
(Pessoalmente, eu não uso o Gmail por causa desse tipo de comportamento, mas reconheço que alguns podem não ter escolha no assunto e outros podem gostar de usá-lo.)