Delta Chat was deleting non-DC messages

Delta Chat version 1.28.1

Expected behavior

No messages deleted at all, not sure why any would be.

Actual behavior

systematic deletion of certain emails - not random, not all but I’m not sure what the selection criterion were.

DC would delete a daily system summary email in my inbox, delete zabbix trouble reports on a similar topic from a another folder, delete all the camera generated alerts (via a different sendmail host) from a third.

Note this was not a “move” operation, it was a “delete” operation per Dovecot logs

:Info: delete: box=

Deleting Delta Chat resolved the issue.

I’m willing to risk reinstalling it to pull debug logs, the messages being deleted happened to fall into “annoyance” rather than “catastrophe” status, but as I’m not sure how I got lucky with a rather minimal delete operation, I’m a bit concerned about reinstalling.

Could this be an artifact of disappearing messages or something? What configurations might lead to a “delete” request?

This likely happened to messages without Message-ID as they were treated as duplicates: Some e-mails are deleted · Issue #3094 · deltachat/deltachat-core-rust · GitHub

The bug was fixed in core 1.77.0. Delta Chat Android has this fix in versions >= v1.30.0.

We have got rid of duplicate detection completely because it caused problems also in cases when user manually copied or moved messages:

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Um… OMG. so that was catastrophic, but thanks for the heads up. I connected this app to a mailstore with a few decades of mail. With the benefit of the warning that any message without a MESSAGE-ID header might have been deleted, I see it deleted possibly 100’s of thousands of critical historical messages back to the late 1990s. I’ll see what I can do from backups… that’s easily days worth of recovery.

Do you know when this catastrophic bug was introduced? Was it with 1.28.1 or earlier?

Just a bit of advice. NEVER EVER EVER perform an irreversible action on a mail store without explicit, per message confirmation. This is a very painful lesson. Ouch.

It appears I first installed Delta-Chat around 2021-05-30, that’s a year of lost messages which are probably non-recoverable by any means, but please let us know when the “delete your old mail without notification or asking” bug was introduced so I know how far back to dig for backups. I’m very annoyed, I had a local IMAP store that wasn’t modified from 2019 to Jan 2020 that would have had the old records, but will have since synchronized the deletion Armageddon.

It was introduced in core 1.71.0, so the bug was present starting from Android version 1.27.0 and until 1.30.0. If you only installed non-beta versions with even version numbers, this means the bug was only in 1.28.x versions, released in January of 2022.

The bug only affects new messages, archived messages that you received before are not affected. Delta Chat only downloads last 100 messages when you configure new account and starting from that point makes decision only on new messages.

that’s helpful - if we trust that filter worked (and I don’t have any reason to doubt it) then only messages from 2022-03-08 to present might have been subject to silent and arbitrary deletion. I have a full mailbox backup from 2020-05 and from 2021-08, the former from before installing delta chat at all, the latter from before 1.27.0. If I find any evidence of older mail being deleted, I’ll report it as it might help others who also suffered mail destruction.

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