Re: Dovecot 2.4.5 on macOS 27 ARM64: post-authentication IMAP connection closes

5 Oct 2026


      --- BEGIN doveconf -n ---
Sanitized output of: doveconf -n
Original preserved unchanged. Operational settings and paths relevant to the
failure are retained; domain, database, and account identifiers are replaced.
2.4.5 (): /opt/dovecot/etc/dovecot/dovecot.conf
Pigeonhole version 2.4.5 (742bb892)
OS: Darwin 27.0.0 arm64
Hostname: example.test
3 default setting changes since version 2.4.5
dovecot_config_version = 2.4.5
auth_debug = yes
auth_mechanisms = login plain cram-md5
auth_username_format = %{user}
base_dir = /var/run/dovecot
default_internal_group = staff
default_internal_user = _dovecot
default_login_user = _dovenull
default_vsz_limit = unlimited
dovecot_storage_version = 2.4.5
first_valid_gid = 350
first_valid_uid = 350
imapsieve_url = sieve://127.0.0.1:4190
log_path = /private/var/log/dovecot-info.log
mail_debug = yes
mail_driver = maildir
mail_gid = vmail
mail_log_prefix = "%{service}(pid %{process:pid} user %{user}): "
mail_path = ~/Maildir
mail_uid = vmail
postmaster_address = postmaster@example.test
protocols {
imap = yes
lmtp = yes
sieve = yes
}
quota_driver = maildir
sendmail_path = /opt/homebrew/sbin/sendmail
sieve_global_extensions {
vnd.dovecot.pipe = yes
vnd.dovecot.environment = yes
}
sieve_pipe_bin_dir = /private/var/dovecot/sieve
sieve_plugins {
sieve_imapsieve = yes
sieve_extprograms = yes
}
sql_driver = mysql
verbose_proctitle = yes
service stats {
unix_listener stats-writer {
group = vmail
mode = 0600
user = vmail
}
}
event_exporter imap_id_log {
driver = log
format = json
}
metric imap_id {
exporter = imap_id_log
fields = id_param_name id_param_version id_param_os id_param_vendor
filter = event=imap_id_received
}
protocol sieve {
info_log_path = /var/log/dovecot-sieve.log
log_path = /var/log/dovecot-sieve-errors.log
managesieve_notify_capability = mailto
}
service lmtp {
executable = lmtp -L
unix_listener lmtp {
mode = 0600
user = exim
}
}
namespace inbox {
inbox = yes
separator = /
mailbox Archive {
auto = subscribe
special_use = "\\Archive"
}
mailbox Drafts {
auto = subscribe
special_use = "\\Drafts"
}
mailbox Junk {
auto = subscribe
autoexpunge = 15 days
special_use = "\\Junk"
sieve_script report-spam {
cause = copy
path = /private/var/dovecot/sieve/report-spam.sieve
type = before
}
}
imapsieve_from Junk {
sieve_script report-ham {
cause = copy
path = /private/var/dovecot/sieve/report-ham.sieve
type = before
}
}
mailbox Sent {
auto = subscribe
special_use = "\\Sent"
}
mailbox Trash {
auto = subscribe
autoexpunge = 30 days
special_use = "\\Trash"
quota_ignore = yes
}
}
service imap {
client_limit = 1
}
protocol lmtp {
info_log_path = /private/var/log/dovecot-lmtp-info.log
log_path = /private/var/log/dovecot-lmtp-errors.log
mail_plugins {
quota = yes
sieve = yes
}
}
service quota-warning {
executable = script /opt/dovecot/bin/quota-warning.sh
user = vmail
unix_listener quota-warning {
group = vmail
mode = 0600
user = vmail
}
}
sieve_script default-before {
path = /private/var/dovecot/sieve/default.sieve
type = before
}
quota "User quota" {
storage_size = 18G
quota_warning warn-95 {
quota_storage_percentage = 95
execute quota-warning {
args = 95 %{user}
}
}
}
protocol imap {
imap_metadata = yes
mail_plugins {
quota = yes
imap_quota = yes
imap_sieve = yes
}
}
mail_attribute {
dict file {
path = %{home}/Maildir/dovecot-attributes
}
}
service managesieve {
process_limit = 1024
}
ssl_server {
cert_file = /private/etc/certificates/example.test.crt
key_file = # hidden, use -P to show it
}
mysql /tmp/mysql.sock {
dbname = maildb
password = # hidden, use -P to show it
user = mail_reader
}
passdb sql {
default_password_scheme = PLAIN
query = SELECT username AS user, clear AS password FROM users WHERE username = '%{user}'
}
userdb static {
fields {
gid = 350
home = /private/var/mail/%{user | domain}/%{user}
uid = 350
}
}
--- END doveconf -n ---
--- BEGIN shortened 2.3/2.4 comparison ---
Dovecot 2.3.21.1 vs 2.4.5: Apple Mail post-authentication comparison
Environment

macOS / Darwin 27.0.0 arm64
Apple Mail 16.0 (3901.100.1.1.12)
TLS with CRAM-MD5
Same client, account data, public-IP/hairpin path, Maildir, and
base_dir=/var/run/dovecot
Only one Dovecot version running at a time

Dovecot 2.3.21.1: successful baseline (shortened)
Oct 02 08:06:50 master: Info: Dovecot v2.3.21.1 (d492236fa0) starting up for lmtp, sieve, imap (core dumps disabled)
Oct 02 08:06:59 imap-login: Info: ID sent: name=Mac OS X Mail, version=16.0 (3901.100.1.1.12), os=Mac OS X, os-version=27.0.1 (26A434), vendor=Apple Inc.: user=<>, rip=203.0.113.10, lip=203.0.113.10, TLS
Oct 02 08:06:59 imap-login: Info: Login: user=<user@example.test>, method=CRAM-MD5, rip=203.0.113.10, lip=203.0.113.10, mpid=56853, TLS
Oct 02 08:06:59 imap(pid 56853 user user@example.test): Debug: Effective uid=350, gid=350, home=/private/var/mail/<domain>/<user>
Oct 02 08:06:59 imap(pid 56853 user user@example.test): Debug: Namespace inbox: type=private, prefix=, sep=/, inbox=yes, hidden=no, list=yes, subscriptions=yes location=maildir:/private/var/mail/<domain>/<user>/Maildir
Oct 02 08:06:59 imap(pid 56853 user user@example.test): Debug: Mailbox INBOX: Mailbox opened
Oct 02 08:06:59 imap(pid 56853 user user@example.test): Debug: Mailbox Junk: Mailbox opened
Oct 02 08:06:59 imap(pid 56853 user user@example.test): Debug: Mailbox Sent: Mailbox opened
Oct 02 08:06:59 imap(pid 56853 user user@example.test): Info: Disconnected: Logged out in=269 out=38460 deleted=0 expunged=0 trashed=0 hdr_count=6 hdr_bytes=35888 body_count=0 body_bytes=0
[Message-open lines omitted from this short excerpt. The original log also
shows Apple Mail reading complete messages and a second normal logout with
in=288 out=42389 body_count=6 body_bytes=38415.]
Dovecot 2.4.5: failure (one of two identical attempts, shortened)
Oct 05 09:37:35 master: Info: Dovecot v2.4.5 () starting up for imap, lmtp, sieve (core dumps disabled)
Oct 05 09:41:11 stats: Info: {"event":"imap_id_received","hostname":"example.test","fields":{"id_param_name":"Mac OS X Mail","id_param_version":"16.0 (3901.100.1.1.12)","id_param_os":"Mac OS X","id_param_vendor":"Apple Inc."}}
Oct 05 09:41:11 auth(user@example.test,203.0.113.10,sasl:cram-md5)<SESSION-1>: Debug: sasl(cram-md5): Finished passdb credentials lookup (status=ok)
Oct 05 09:41:11 auth(user@example.test,203.0.113.10,sasl:cram-md5)<SESSION-1>: Debug: sasl(cram-md5): Interaction succeeded
Oct 05 09:41:11 auth: Debug: master userdb out: USER <request-id> user@example.test uid=350 gid=350 home=/private/var/mail/<domain>/<user> auth_mech=CRAM-MD5 auth_token=<redacted-auth-token> local_name=example.test
Oct 05 09:41:11 imap-login: Info: Logged in: user=<user@example.test>, method=CRAM-MD5, rip=203.0.113.10, lip=203.0.113.10, mpid=57601, TLS, session=<SESSION-1>
Oct 05 09:41:12 imap(pid 57601 user user@example.test): Debug: Effective uid=350, gid=350, home=/private/var/mail/<domain>/<user>
Oct 05 09:41:12 imap(pid 57601 user user@example.test): Debug: Namespace inbox: type=private, prefix=, sep=/, inbox=yes, hidden=no, list=yes, subscriptions=yes
Oct 05 09:41:12 imap(pid 57601 user user@example.test): Debug: maildir++: root=/private/var/mail/<domain>/<user>/Maildir, index=, indexpvt=, control=, inbox=/private/var/mail/<domain>/<user>/Maildir, alt=
Oct 05 09:41:12 imap(pid 57601 user user@example.test): Info: Disconnected: Connection closed (No commands sent) in=0 out=502 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Observed boundary
Both versions complete TLS, CRAM-MD5, userdb lookup, privilege selection,
namespace setup, and Maildir path resolution. Under 2.3, Apple Mail proceeds to
mailbox commands. Under 2.4, the authenticated IMAP process sends 502 bytes and
the connection closes before that process records any client command. A second
2.4 attempt repeats the same in=0 out=502 result. No panic, fatal error, signal,
or explicit anvil error appears in the captured interval.
Relevant process-model difference
2.3:
service imap {
process_limit = 200
client_limit = 5
service_count = 0
}
2.4:
service imap {
client_limit = 1
}
This is noted as a diagnostic difference, not asserted as the cause.
--- END shortened 2.3/2.4 comparison ---

Re: Dovecot 2.4.5 on macOS 27 ARM64: post-authentication IMAP connection closes

George

Sanitized output of: doveconf -n

Original preserved unchanged. Operational settings and paths relevant to the

failure are retained; domain, database, and account identifiers are replaced.

2.4.5 (): /opt/dovecot/etc/dovecot/dovecot.conf

Pigeonhole version 2.4.5 (742bb892)

OS: Darwin 27.0.0 arm64

Hostname: example.test

3 default setting changes since version 2.4.5

--- BEGIN shortened 2.3/2.4 comparison --- Dovecot 2.3.21.1 vs 2.4.5: Apple Mail post-authentication comparison

Environment

Dovecot 2.3.21.1: successful baseline (shortened)

Dovecot 2.4.5: failure (one of two identical attempts, shortened)

Observed boundary

Relevant process-model difference