Replying to: https://dovecot.org/pipermail/dovecot/2022-May/124816.html Hi, Looking at the code (and tested via local build from source) it looks like doveadm deduplicate in 2.3.19 can cause significant data loss. A 2022-02-11 commit removed key duplication resulting in undefined behaviour which is often truncation of a mailbox to 67 entries. (HASH_TABLE_MIN_SIZE) https://github.com/dovecot/core/commit/320844f50cd669b602d30210e2e5216f65d20... diff --git a/src/doveadm/doveadm-mail-deduplicate.c b/src/doveadm/doveadm-mail-deduplicate.c index caec758112..2152482876 100644 --- a/src/doveadm/doveadm-mail-deduplicate.c +++ b/src/doveadm/doveadm-mail-deduplicate.c @@ -63,8 +63,10 @@ cmd_deduplicate_box(struct doveadm_mail_cmd_context *_ctx, if (key != NULL && *key != '\0') { if (hash_table_lookup(hash, key) != NULL) mail_expunge(mail); - else + else { + key = p_strdup(pool, key); hash_table_insert(hash, key, POINTER_CAST(1)); + } } }