Log Message:
Changes 2.2.28:
* director: "doveadm director move" to same host now refreshes user's
  timeout. This allows keeping user constantly in the same backend by
  just periodically moving the user there.
* When new mailbox is created, use initially INBOX's
  dovecot.index.cache caching decisions.
* Expunging mails writes GUID to dovecot.index.log now only if the
  GUID is quickly available from index/cache.
* pop3c: Increase timeout for PASS command to 5 minutes.
* Mail access errors are no longer ignored when searching or sorting.
  With IMAP the untagged SEARCH/SORT reply is still sent the same as
  before, but NO reply is returned instead of OK.

+ Make dovecot.list.index's filename configurable. This is needed when
  there are multiple namespaces pointing to the same mail root
  (e.g. lazy_expunge namespace for mdbox).
+ Add size.virtual to dovecot.index when folder vsizes are accessed
  (e.g. quota=count). This is mainly a workaround to avoid slow quota
  recalculation performance when message sizes get lost from
  dovecot.index.cache due to corruption or some other reason.
+ auth: Support OAUTHBEARER and XOAUTH2 mechanisms. Also support them
  in lib-dsasl for client side.
+ auth: Support filtering by SASL mechanism: passdb { mechanisms }
+ Shrink the mail processes' memory usage by not storing settings
  duplicated unnecessarily many times.
+ imap: Add imap_fetch_failure setting to control what happens when
  FETCH fails for some mails (see example-config).
+ imap: Include info about last command in disconnection log line.
+ imap: Created new SEARCH=X-MIMEPART extension. It's currently not
  advertised by default, since it's not fully implemented.
+ fts-solr: Add support for basic authentication.
+ Cassandra: Support automatically retrying failed queries if
  execution_retry_interval and execution_retry_times are set.
+ doveadm: Added "mailbox path" command.
+ mail_log plugin: If plugin { mail_log_cached_only=yes }, log the
  wanted fields only if it doesn't require opening the email.
+ mail_vsize_bg_after_count setting added (see example-config).
+ mail_sort_max_read_count setting added (see example-config).
+ pop3c: Added pop3c_features=no-pipelining setting to prevent using
  PIPELINING extension even though it's advertised.

- Index files: day_first_uid wasn't updated correctly since v2.2.26.
  This caused dovecot.index.cache to be non-optimal.
- imap: SEARCH/SORT may have assert-crashed in
  client_check_command_hangs
- imap: FETCH X-MAILBOX may have assert-crashed in virtual mailboxes.
- imap: Running time in tagged command reply was often wrongly 0.
- search: Using NOT n:* or NOT UID n:* wasn't handled correctly
- director: doveadm director kick was broken
- director: Fix crash when using director_flush_socket
- director: Fix some bugs when moving users between backends
- imapc: Various error handling fixes and improvements
- master: doveadm process status output had a lot of duplicates.
- autoexpunge: If mailbox's rename timestamp is newer than mail's
  save-timestamp, use it instead. This is useful when autoexpunging
  e.g. Trash/* and an entire mailbox is deleted by renaming it under
  Trash to prevent it from being autoexpunged too early.
- autoexpunge: Multiple processes may have been trying to expunge the
  same mails simultaneously. This was problematic especially with
  lazy_expunge plugin.
- auth: %{passdb:*} was empty in auth-worker processes
- auth-policy: hashed_password was always sent empty.
- dict-sql: Merge multiple UPDATEs to a single statement if possible.
- fts-solr: Escape {} chars when sending queries
- fts: fts_autoindex_exclude = \Special-use caused crashes
- doveadm-server: Fix leaks and other problems when process is reused
  for multiple requests (service_count != 1)
- sdbox: Fix assert-crash on mailbox create race
- lda/lmtp: deliver_log_format values weren't entirely correct if Sieve
  was used. especially %{storage_id} was broken.
- lmtp_user_concurrency_limit didn't work if userdb changed username