Upgrading Dovecot CE from 2.3 to 2.3.x

Dovecot CE

v2.3.x to v2.3.14

• Removed cydir storage format. It was never intended for production use.
• Removed snarf plugin. It was for UW-IMAP's mbox compatibility, which is unlikely to be needed anymore.
• Removed mail_filter plugin. It was mainly intended as an example plugin.

Dovecot Core

v2.3.x to v2.3.7

• fts-solr: The obsolete break-imap-search parameter is no longer recognized

v2.3.x to v2.3.12

• Event filter syntax has changed, see Event Filtering.

v2.3.x to v2.3.14

• Removed autocreate plugin. Use mailbox { auto } instead.
• Removed expire plugin. Use mailbox { autoexpunge } instead.
• Removed xz write support from zlib plugin. (Reading xz compressed mails is still supported.) Use another compression algorithm.

v2.3.x to v2.3.15

• ssl_min_protocol default changed to TLSv1.2, as older TLS versions are deprecated (see RFC 8996). Change it to TLSv1 or TLSv1.1 if you need to support older, deprecated protocols.
• The 'SNIPPET' and 'PREVIEW (w/explicit algorithm selection)' IMAP commands have been deprecated. The new RFC 8970 compliant PREVIEW command should be exclusively used in the future.
• fs-compress plugin now accept per-algorithm value.
• plugin-zlib <plugin-mail-compress> now accepts per-algorithm value.
• plugin-imap-zlib now uses per-algorithm compression level settings. The old setting is ignored.

v2.3.x to v2.3.16

• auth_worker service service service_count setting has been changed.

v2.3.x to v2.3.20

• fts_stopwords_workaround has been introduced.

  The default for the setting, auto, activates some mitigations for the problem of some searches failing to retrieve the expected result when stopwords and multiple languages are used together. To revert to the pre 2.3.20 behavior, set fts_stopwords_workaround = no.