March 2021 - dovecot - dovecot.org

FTS solr or xapian and Public Folders
by David Williams 13 May '22

13 May '22

Hi all I hope someone can help with this. I'm looking at setting up FTS on a Dovecot server which has some quite big pubic folders (100,000+ emails each) and would appreciate some info about how fts both Xapian and Solr works with public folders. As background of the folders can receive emails and I use a dummy user and an alias file to deliver them for example testfolder: dummy+Public/MYTESTFOLDER(a)example.com delivers email addressed to testfolder(a)example.com to MYTESTFOLDER in the namespace Public. Has anyone successfully setup FTS with public folders using either Xapian or Solr and what happens when one user changes a folder, does that change show up for other users? E.G.: When an email is delivered by dummy and indexed will that email be indexed for other users as well? Similarly what happens that when an email is moved between, deleted from or copied to public folders by one user will that change then show up for the other users or not? I guess the basic question is: Are public folders indexed once and then the indexes are made available to each user with access or are they indexed for each user? Any info or experience that anyone has will be appreciated. Many thanks David

2 1

test-file-cache.c needs #ifdef HAVE_RLIMIT_AS
by Rupert Gallagher 07 Feb '22

07 Feb '22

test-file-cache.c:259:24: error: use of undeclared identifier 'RLIMIT_AS' test_assert(getrlimit(RLIMIT_AS, &rl_cur) == 0); ^ test-file-cache.c:267:24: error: use of undeclared identifier 'RLIMIT_AS' test_assert(setrlimit(RLIMIT_AS, &rl_new) == 0); ^ test-file-cache.c:270:24: error: use of undeclared identifier 'RLIMIT_AS' test_assert(setrlimit(RLIMIT_AS, &rl_cur) == 0); ^ test-file-cache.c:276:24: error: use of undeclared identifier 'RLIMIT_AS' test_assert(setrlimit(RLIMIT_AS, &rl_new) == 0); ^ test-file-cache.c:279:24: error: use of undeclared identifier 'RLIMIT_AS' test_assert(setrlimit(RLIMIT_AS, &rl_cur) == 0); ^

3 9

Dsync replication - delayed replication (Sync lock)
by Daniel Botting 31 Jan '22

31 Jan '22

Hi, *Our setup:* Two Debian 10 machines that are setup to replicate mail between them, we have round robin DNS setup so a user can connect to either server. *What should happen:* Mail is delivered to either server and replicated across straight away to their mailbox on the other server so it does not matter which one they are connected to they will receive it fairly soon after delivery. *What actually happens:* In some instances the user will experience a delayed receipt of messages if they are not connected to the server that the message is initially delivered to, sometimes the delay is 5/10 minutes, we had a recent support ticket submitted where it was over an hour. Error message seen in mail.err: Sep 1 10:16:15 <host name> dovecot: dsync-local(<username>)<WELSGEERTl8FEAAAZJ7A9A>: Error: Couldn't lock /path/to/mailbox/.dovecot-sync.lock: fcntl(/path/to/mailbox/.dovecot-sync.lock, write-lock, F_SETLKW) locking failed: Timed out after 30 seconds (WRITE lock held by pid 3697) Process 3697 is dovecot/doveadm-server. *Doveconf -n output:* # 2.3.10.1 (a3d0e1171): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.10 (67bf5bd7) # OS: Linux 4.19.0-10-amd64 x86_64 Debian 10.5 # Hostname: <server hostname> auth_verbose = yes default_vsz_limit = 0 doveadm_password = # hidden, use -P to show it first_valid_gid = 8 first_valid_uid = 8 last_valid_gid = 8 last_valid_uid = 8 lda_mailbox_autocreate = yes lda_mailbox_autosubscribe = yes mail_gid = 8 mail_location = maildir:~/Maildir mail_plugins = " notify replication" mail_uid = 8 managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex im ap4flags copy include variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext editheader imapfla gs namespace inbox { inbox = yes location = mailbox Drafts { special_use = \Drafts } mailbox Junk { special_use = \Junk } mailbox Sent { special_use = \Sent } mailbox "Sent Messages" { special_use = \Sent } mailbox Trash { special_use = \Trash } prefix = } passdb { args = /etc/dovecot/dovecot-ldap.conf.ext driver = ldap } plugin { mail_replica = tcps:<server being replicated to>:<port being used> sieve = ~/.dovecot.sieve sieve_dir = ~/sieve sieve_extensions = +editheader +imapflags } postmaster_address = postmaster@<domain address> protocols = " imap sieve pop3" replication_max_conns = 12 service aggregator { fifo_listener replication-notify-fifo { user = mail } unix_listener replication-notify { user = mail } } service auth { unix_listener /var/run/dovecot-exim-bridge { mode = 0660 user = Debian-exim } } service doveadm { inet_listener { port = <port being used for replication> ssl = yes } } service imap-login { inet_listener imap { port = 143 } } inet_listener imaps { port = 993 ssl = yes } process_limit = 512 process_min_avail = 4 service_count = 1 } service imap { process_limit = 1024 } service managesieve-login { inet_listener sieve { port = <sieve port> } process_min_avail = 1 service_count = 8 vsz_limit = 256 M } service managesieve { process_limit = 1024 } service replicator { process_min_avail = 1 unix_listener replicator-doveadm { mode = 0666 } } ssl = required ssl_cert = </path/to/ssl/cert/fullchain.pem ssl_cipher_list = ALL:!LOW:!SSLv2:!EXP:!aNULL ssl_client_ca_dir = /etc/ssl/certs ssl_key = # hidden, use -P to show it ssl_min_protocol = TLSv1.2 userdb { args = /etc/dovecot/dovecot-ldap.conf.ext driver = ldap override_fields = home=/var/mail/%u uid=mail gid=mail } protocol lda { mail_plugins = " notify replication sieve" } protocol imap { mail_max_userip_connections = 32 mail_plugins = " notify replication" } protocol sieve { mail_max_userip_connections = 10 managesieve_logout_format = bytes=%i/%o managesieve_max_line_length = 65536 } Kind regards Daniel

3 3

sieve - segmentation fault
by kjonca＠o2.pl 01 Dec '21

01 Dec '21

I tried to experiment with "index" extension and I found that, in case "0" sieve-filter segfaults. example code was: --8<---------------cut here---------------start------------->8--- if header :index 0 :last :regex "received" "some regex here" { fileinto "dedicated mailbox" ; } --8<---------------cut here---------------end--------------->8--- KJ -- http://stopstopnop.pl/stop_stopnop.pl_o_nas.html I dote on his very absence. -- William Shakespeare, "The Merchant of Venice"

2 2

maildirfolder file created in maildir root during auto-creation with 2.3.4.1 but not 2.2.27
by Christian Balzer 02 Sep '21

02 Sep '21

Hello, as the tin says. I have several servers running 2.2.27 (Debian stretch) and am adding new ones with 2.3.4.1 (Debian buster). The configs were upgraded where needed but neither 10-mail.conf nor 15-mailboxes.conf were changed. 15-mailboxes is all commented out (I guess the default is auto-create, which isn't documented anywhere I could find) and the only non-comments in 10-mail.conf are --- mail_location = maildir:%h mail_privileged_group = mail --- So yes, no namespaces are explicitly defined/declared. The 2.3.4.1 version wrongly creates a maildirfolder file in the home directory (maildir root), preventing exim from correctly creating/using maildirsize. a) Is this expected behavior and can it be changed? b) How can I disable inbox auto-creation if a) doesn't pan out? Thanks, Christian -- Christian Balzer Network/Systems Engineer chibi(a)gol.com Rakuten Mobile Inc.

2 5

BUG REPORT: MAIL-CRYPT plugin: doveadm mailbox cryptokey -O option
by ean365 17 Aug '21

17 Aug '21

Aki: I have identified a bug in the "*-O*" option of "*doveadm mailbox cryptokey password*" plugin command -- it is expecting an argument, but it is supposed to be a boolean option. I have also identified the (simple) fix to the source on github... /I am a dovecot community noob, so please forgive me if this has already been identified... (if so, I hope it gets fixed soon)... / The "-O" option in *struct doveadm_cmd_mcp_key_password* is set to expect a *STR* parameter, but it should be *BOOL*. See line 1027 in plugins/mail-crypt/doveadm-mail-crypt.c of master branch... Currently: ***DOVEADM_CMD_PARAM**(**'O'**, **"ask-old-password"**, CMD_PARAM_STR, **0**) *Should be: ***DOVEADM_CMD_PARAM**(**'O'**, **"ask-old-password"**, CMD_PARAM_BOOL, **0**)* Workaround is to specify *-O* last on command line with a dummy argument, like this: *doveadm mailbox cryptokey password -N -O ""* Also, a quick question and suggestion -- Why does the *doveadm mailbox cryptokey password* command not ask for a new password twice, with a check that both entries must match before the password is changed? The last thing we would want is to type something wrong accidentally, and change the new password to something unknown -- rendering encrypted email unrecoverable. I would like to suggest that the code in *cmd_mcp_key_password_run* be amended to include verifying password entry twice. (I am writing a simple addition to postfixadmin that changes the user's mail-crypt password whenever they use postfixadmin to change their login password. It calls *doveadm* to change the keys. I came across this bug while working through this.) Thanks for all your help! Eric **

2 5

How to use xapian with non-text attachments
by André Rodier 03 Jul '21

03 Jul '21

Hello, I am developing a hosting platform on Debian Bullseye, with Dovecot amongst other tools. I am trying to use the xapian full test search plugin, but I can see the attachments are skipped: This is what I have in the logs when running the indexing in verbose mode: ----------------------------------------------------------------------- doveadm(camille): Info: FTS Xapian: fts_backend_xapian_check_access doveadm(camille): Info: FTS Xapian: Memory stats : Used = 56 MB, Free = 66 MB doveadm(camille): Info: FTS Xapian: fts_backend_xapian_index_hdr doveadm(camille): Info: FTS Xapian: fts_backend_xapian_query doveadm(camille): Info: FTS Xapian: Query= uid:"44" doveadm(camille): Info: FTS Xapian: Ngram(S) -> 63 items (total 0 KB) doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_unset_build_key doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Message- Id,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_build_more doveadm(camille): Info: FTS Xapian: fts_backend_xapian_check_access doveadm(camille): Info: FTS Xapian: Memory stats : Used = 56 MB, Free = 66 MB doveadm(camille): Info: FTS Xapian: fts_backend_xapian_index_hdr doveadm(camille): Info: FTS Xapian: fts_backend_xapian_query doveadm(camille): Info: FTS Xapian: Query= uid:"44" doveadm(camille): Info: FTS Xapian: Ngram(XMID) -> 4 items (total 0 KB) doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_unset_build_key doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=X- Mailer,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'xmailer' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=MIME- Version,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'mimeversion' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Content- Type,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'contenttype' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Authentication- Results,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'authenticationresults' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=X-AV- Checked,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'xavchecked' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Content- Type,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'contenttype' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=(null),Type=text/plain,Disposition=(null)) doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_build_more doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_unset_build_key doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Content- Type,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'contenttype' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Content- Description,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'contentdescription' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Content- Disposition,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'contentdisposition' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=Content-Transfer- Encoding,Type=(null),Disposition=(null)) doveadm(camille): Info: FTS Xapian: Unknown header (indexing) 'contenttransferencoding' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_build_key doveadm(camille): Info: FTS Xapian: New part (Header=(null),Type=text/csv,Disposition=attachment; filename="file.csv") doveadm(camille): Info: FTS Xapian: Skipping part of type 'text/csv' and disposition 'attachment; filename="file.csv"' doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_set_mailbox doveadm(camille): Info: FTS Xapian: Unset box 'INBOX' (c0d4e304584e5460dae30000075d7e67) doveadm(camille): Info: FTS Xapian: fts_backend_xapian_oldbox doveadm(camille): Info: FTS Xapian: Done indexing 'INBOX' (c0d4e304584e5460dae30000075d7e67) (13 msgs in 261 ms, rate: 49.8) doveadm(camille): Info: FTS Xapian: fts_backend_xapian_release (unset_box) doveadm(camille): Info: FTS Xapian: Committed 'unset_box' in 17 ms doveadm(camille): Info: FTS Xapian: Box is empty doveadm(camille): Info: FTS Xapian: fts_backend_xapian_update_deinit (/home/users/camille/mails/indexes/xapian-indexes) doveadm(camille): Info: FTS Xapian: fts_backend_xapian_release (update_deinit) doveadm(camille): Info: FTS Xapian: Committed 'update_deinit' in 0 ms doveadm(camille): Info: FTS Xapian: Deinit /home/users/camille/mails/indexes/xapian-indexes) ----------------------------------------------------------------------- Especially thos line: doveadm(camille): Info: FTS Xapian: Skipping part of type 'text/csv' and disposition 'attachment; filename="file.csv"' I have seen this as a bug on fts-xapian: https://github.com/grosjo/fts-xapian/issues/68 Which then references a PR on Dovecot core itself: https://github.com/dovecot/core/pull/155 Any idea on how to use xapian with non-text attachments ? Thanks a lot for your help! André

2 2

Mailbox problem on centos O/S after some "fiddling"
by John Richards 28 May '21

28 May '21

Good day from Somerset, England Version 2.2.10 Problem after a huge centos update Data:- Server has 8 mailboxes under /var/mail/"user name" history:- After update, mail to ONE user was going into mqueue as undeliverable Had to delete and recreate the user. somewhere along the line (ME!) /var/mail/;imap var/mail/new were deleted After new user and reboot server no one could access mailboxes with password error except ONE user randomly....This created the /var/mail/.mbox folder and sub folders but with the owner as the user name. Then any mail for other users was put in the /var/new folder and just sat there. only the "owner" of this folder could get mail, everyone else was prohibited with password error. chown the folder (owner:group) to root did nothing BUT When .mbox was give PUBLIC execute permissions (771) suddenly everything works fine! I do not understand why dovecot creates this folder as we ONLY ever use pop3 (currently with plain text auth but going to secure when this sorted) for mail and also why when it writes the blank folder it "owns" it with the user accessing it (also the /var/mail/new folder takes the same owner) I have trolled everywhere and spent a whole day on this so any clues would be very gratefully accepted as do not like to leave this folder as 771 (note the folder INBOX within it is only 770 and the log file in that is 660) Is this INBOX needed at all for pop3 ? rgds John Richards UK ================= dovecot -n # 2.2.10: /etc/dovecot/dovecot.conf # OS: Linux 3.10.0-514.2.2.el7.x86_64 x86_64 CentOS Linux release 7.3.1611 (Core ) ext4 auth_mechanisms = plain login disable_plaintext_auth = no mail_location = mbox:/var/mail/:INBOX=/var/mail/%u mbox_write_locks = fcntl namespace inbox { inbox = yes location = mailbox Drafts { special_use = \Drafts } mailbox Junk { special_use = \Junk } mailbox Sent { special_use = \Sent } mailbox "Sent Messages" { special_use = \Sent } mailbox Trash { special_use = \Trash } prefix = } passdb { driver = shadow } protocols = pop3 service imap-login { inet_listener imap { port = 143 } inet_listener imaps { port = 993 ssl = yes } } ssl_cert = </etc/pki/tls/certs/watchetwebdesign.co.uk.crt ssl_key = </etc/pki/tls/private/watchetwebdesign.co.uk.key userdb { driver = passwd }

2 1

[Dovecot] Doveadm sometimes failed "to iterate through some users" after upgrade to 2.2
by Alessio Cecchi 03 May '21

03 May '21

Hi, I'm running every week in cron "doveadm expunge -A mailbox Spam before 30d" and monthly "doveadm quota recalc -A". After the upgrade to dovecot 2.2.12 (from 2.1.17), "doveadm -A" sometimes exit with this error: doveadm(user(a)domain.com): Error: User listing returned failure doveadm: Error: Failed to iterate through some users # echo $? 75 If I re-run the same command the user where doveadm stops changeing (always in alphabetical order): info@ mario@ pippo@ zazza@ and finally, after 3 or 4 run, ends with success. I have enable debug (via doveadm -D and auth/mail debub in 10-logging.con) but there are no errors or difference in the log when doveadm exit with the error (error code is 75). If I run # doveadm expunge -A mailbox Spam savedbefore 30d doveadm works fine Can somebody help me? Here is my configuration: # dovecot -n # 2.2.12: /etc/dovecot/dovecot.conf # OS: Linux 2.6.32-5-amd64 x86_64 Debian 6.0.9 auth_debug = yes auth_master_user_separator = * auth_verbose = yes deliver_log_format = msgid=%m, from=%f, subject="%s": %$ dict { expire = mysql:/etc/dovecot/dovecot-dict-sql.conf.ext sqlquota = mysql:/etc/dovecot/dovecot-dict-sql.conf.ext } disable_plaintext_auth = no dotlock_use_excl = no first_valid_gid = 89 first_valid_uid = 89 imap_client_workarounds = delay-newmail tb-extra-mailbox-sep tb-lsub-flags imap_idle_notify_interval = 29 mins imap_logout_format = in=%i out=%o session=<%{session}> last_valid_gid = 89 last_valid_uid = 89 lda_mailbox_autocreate = yes lda_mailbox_autosubscribe = yes listen = * mail_debug = yes mail_fsync = always mail_location = maildir:~/Maildir mail_nfs_index = yes mail_nfs_storage = yes mail_plugins = quota expire maildir_very_dirty_syncs = yes managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave vnd.dovecot.duplicate mmap_disable = yes namespace { list = children location = maildir:%%h/Maildir:INDEX=~/Maildir/shared/%%u prefix = shared/%%n/ separator = / subscriptions = no type = shared } namespace inbox { inbox = yes location = mailbox Drafts { auto = subscribe special_use = \Drafts } mailbox Sent { auto = subscribe special_use = \Sent } mailbox "Sent Messages" { special_use = \Sent } mailbox Spam { auto = subscribe special_use = \Junk } mailbox Trash { auto = subscribe special_use = \Trash } prefix = separator = / } passdb { args = username_format=%Ld /etc/dovecot/extra/alias-domains-denylogin.txt deny = yes driver = passwd-file } passdb { args = /etc/dovecot/extra/master-users driver = passwd-file master = yes pass = yes } passdb { args = /etc/dovecot/dovecot-sql.conf.ext driver = sql } plugin { expire = Trash expire2 = Spam expire_dict = proxy::expire quota = maildir:UserQuota quota2 = dict:Quota Usage::noenforcing:proxy::sqlquota quota_grace = 10M quota_rule2 = Trash:storage=+100M quota_warning = storage=95%% quota-warning 95 %u quota_warning2 = storage=80%% quota-warning 80 %u sieve = ~/.dovecot.sieve sieve_before = /etc/dovecot/sieve/before.sieve sieve_dir = ~/sieve sieve_extensions = +vnd.dovecot.duplicate -vacation } pop3_client_workarounds = outlook-no-nuls oe-ns-eoh pop3_logout_format = top=%t/%p, retr=%r/%b, del=%d/%m, size=%s, bytes=%i/%o, session=<%{session}> protocols = imap pop3 sieve service auth-worker { process_limit = 1000 } service auth { client_limit = 5500 unix_listener auth-userdb { group = vchkpw mode = 0660 user = vpopmail } } service dict { process_limit = 300 unix_listener dict { group = vchkpw mode = 0660 user = vpopmail } } service imap-login { process_min_avail = 4 service_count = 0 } service imap { process_limit = 4000 service_count = 100 } service managesieve-login { inet_listener sieve { port = 4190 } } service pop3-login { service_count = 0 } service pop3 { process_limit = 1023 service_count = 100 } service quota-warning { executable = script /etc/dovecot/scripts/quota-warning.sh unix_listener quota-warning { user = vpopmail } user = vpopmail } ssl_cert = </etc/dovecot/ssl/wildcard-myemail.net.pem ssl_key = </etc/dovecot/ssl/wildcard-myemail.net.key submission_host = localhost userdb { args = /etc/dovecot/dovecot-sql.conf.ext driver = sql } protocol lda { mail_location = maildir:~/Maildir:INDEX=MEMORY mail_plugins = quota expire sieve } protocol imap { mail_max_userip_connections = 15 mail_plugins = quota expire imap_quota } protocol sieve { mail_max_userip_connections = 2 } protocol pop3 { mail_max_userip_connections = 5 } -- Alessio Cecchi is: @ ILS -> http://www.linux.it/~alessice/ on LinkedIn -> http://www.linkedin.com/in/alessice Assistenza Sistemi GNU/Linux -> http://www.cecchi.biz Cloud Email Hosting -> http://www.qboxmail.com @ PLUG -> ex-Presidente, adesso senatore a vita, http://www.prato.linux.it

3 3

IMAP session hangs on 8k-long commands if COMPRESS=DEFLATE is enabled
by Guilhem Moulin 21 Apr '21

21 Apr '21

Hi there, Dovecot 2.3.7 appears to hang when the client sends a long command after enabling the IMAP COMPRESS extension [RFC 4978]. PoC script attached along with the doveconf(1) output. Without COMPRESS=DEFLATE, and with the default ‘imap_max_line_length’ value (64k) I'm able send commands up to 65539 bytes long (that's 3 bytes more than 2¹⁶, so maybe the leading tag and the trailing CRLF aren't counted), after which Dovecot rightfully replies with tagged BAD responses. $ COMPRESS=n /tmp/many-fetch.pl 65539 […] C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [65539 bytes] S: x OK Fetch completed (0.005 + 0.001 + 0.004 secs). C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [65540 bytes] S: x BAD Error in IMAP command UID FETCH: IMAP command line too large (0.001 + 0.001 secs). C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [65541 bytes] S: x BAD Error in IMAP command UID FETCH: IMAP command line too large (0.001 + 0.001 secs). With COMPRESS=DEFLATE however, the server never sends anything back when the command size exceeds 8192 bytes: $ COMPRESS=y /tmp/many-fetch.pl 8192 […] S: x OK [READ-ONLY] Examine completed (0.001 + 0.000 secs). C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [8191 bytes] S: x OK Fetch completed (0.001 + 0.000 secs). C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [8192 bytes] S: x OK Fetch completed (0.001 + 0.000 secs). C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [8193 bytes] [ _hangs until the server terminates the session for inactivity_ ] S: * BYE Disconnected for inactivity. strace(1) show that Dovecot didn't send the response, even though the server log indicates that it's able to fully read the command. Interestingly, when setting ‘imap_max_line_length’ to 4096, the server also hangs after receiving a command of size >4096 bytes (instead of replying with a tagged BAD response). $ COMPRESS=y /tmp/many-fetch.pl 4096 C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [4095 bytes] S: x OK Fetch completed (0.001 + 0.000 secs). C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [4096 bytes] S: x OK Fetch completed (0.001 + 0.000 secs). C: x UID FETCH 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,… [4097 bytes] [ _hangs until the server terminates the session for inactivity_ ] I'm also able to reproduce the buggy behavior against Dovecot versions found in other Debian releases. It's identical with 2.3.4 (Buster), the server also hang past 8192 bytes. 2.2.27 (Stretch) and 2.2.13 (Jessie) are able to send replies to 8k-long commands, but hang past 65536 bytes. For all 3 releases, without COMPRESS=DEFLATE Dovecot doesn't hang and rightfully sends tagged BAD responses to commands of size >65539 bytes. So while the hanging behavior appears to be a long-standing bug, the fact that's it's now hit at min($imap_max_line_length, 8192) instead of $imap_max_line_length seems to be a regression from somewhere between 2.2.27 and 2.3.4. Cheers, -- Guilhem.

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