The keys used are:
!: modified feature, -: deleted feature, +: new feature
+1.9.0 (2017-09-02):
+
+ + $ssl_verify_partial_chains permits verifying partial certificate chains.
+ This allows the storage of only intermediate/host certificates in the
+ $certificate_file. (OpenSSL 1.0.2b and newer only)
+ ! SNI support added for OpenSSL and GnuTLS.
+ + Choice and confirmation prompts can now wrap across multiple lines.
+ + Window resizes are handled while in the line editor.
+ + "color compose" can color the compose menu header fields and the
+ security status. See "Using Color and Mono Video Attributes" in the
+ manual for more details.
+ + Setting $header_color_partial allows partial coloring of headers in the
+ pager. This can be used to color just the header labels, or strings
+ inside the headers. hdrdefault controls the color of the unmatched part.
+ + When $history_remove_dups is set, duplicates in the history ring will
+ be scanned and removed each time a new entry is added.
+ ! IMAP header downloading was improved to support out-of-order and
+ missing MSN entries.
+ ! $message_cache_clean should be faster for large mailboxes.
+ + Self-encryption can be enabled using the $pgp_self_encrypt,
+ $pgp_self_encrypt_as, $smime_self_encrypt, and $smime_self_encrypt_as
+ options.
+ ! $postpone_encrypt now will use the $pgp_self_encrypt_as or
+ $smime_self_encrypt_as option values first. $postpone_encrypt_as will
+ be checked second, but should be considered deprecated.
+ + $forward_attribution_intro and $forward_attribution_trailer can be used
+ to customize the message preceding and following a forwarded message.
+ + The ~<() and ~>() pattern operators match messages whose immediate parent,
+ or immediate children respectively, match the subpattern inside ().
+ They are more specific versions of the ~() pattern operator.
+ + $imap_poll_timeout allow IMAP mailbox polling to time out. This defaults
+ to 15 seconds.
+ + The attachment menu now supports nested encryption. This allows
+ attachments in nested encrypted messages to be saved or operated on.
+ + $mime_type_query_command specifies a command to run to determine
+ a new attachment's mime type. When $mime_type_query_first is set,
+ this command will be run before looking at the mime.types file.
+
1.8.3 (2017-05-30):
! Bug fix release.