Expected behavior for "Purge Deleted" with IMAP?

[Edd]

I use IMAP with an "inbox.com" account.
If I am in the message list view, press menu, I get a menu which contains an item "Purge Deleted".
Without marking any messages for deletion, if I select "purge deleted", it deletes every message in the folder, including all messages on the server which were not downloaded into A-M. I had maybe 1-2 years of received messages downloaded in A-M. It deleted all 5 years worth of messages from the server.

I would expect a feature named purge deleted to only delete messages for which I have marked for deletion.

Is this a bug or is this the expected behavior?

[Edd]

Apparently the problem I am experiencing is caused by the fact that I was in the "spam" folder.

I have been using the "spam" folder to store messages from non-contacts for 5+ years.
I setup my email service provider to put all messages from contacts in "inbox" otherwise move to "spam". I don't get junk mail, its all messages from online purchases or mailing lists that I was planning on keeping permanently.

I cannot believe there is a feature in an email app that deletes messages that aren't marked for deletion. That does not make sense to me.

The folders [ Drafts ], [ Sent ], and [ Deleted ] have square brackets around them, this help to identify these folders as having special attributes. The behavior these folders should be expected to be different. The folder I use for incoming messages from non-contacts just happens to be called "Spam" and appears as a normal folder. I expect the behavior to be the same as my "Inbox" or any other normal folder.

[Kostya Vasilyev]

"delete all" inside Spam and Deleted folders will delete 1) from the server 2) all messages 3) including those never loaded into the app (this is new in 1.3).

The feature is there based on user requests and is working as intended.

It has a confirmation dialog, enabled by default.

[Kostya Vasilyev]

Right. And to elaborate a bit on why it works this way:

I used to get a lot of emails asking "How to delete all, I mean all, messages in the Trash folder? On the server too? So I never ever see them again?"....

...and that's why it works the way it does.

[Edd]

Thanks Paris!
I am new to using IMAP, so I didn't understand the difference between "sync as incoming" and "sync as spam".
I have changed to spam folder to sync as incoming and now the software behaves the way I expect it to.