But note that disabling bcc_self aka Advanced :: Send Copy to Self breaks multi-device usage, other devices won’t see user’s outgoing messages then.
Maybe we could expose disabling only sync messages for users, but that wouldn’t fix the problem completely because there are other auto-sent messages e.g. SecureJoin ones. All auto-sent messages should be moved to the “DeltaChat” folder regardless of the Move automatically to DeltaChat Folder (mvbox_move) setting (there’s a PR for this: feat: Always move outgoing auto-generated messages to the mvbox by iequidoo · Pull Request #5755 · deltachat/deltachat-core-rust · GitHub), but recent findings in Receiving blank emails with encrypted attachments whenever an email blocked, deleted or accepted show that e.g. for Gmail messages are still shown in Inbox for a while. Though i suggest to discuss this separate problem in that thread.