- dovecot - dovecot.org

Quota Clone not tracking unlimited quota
by Prakash Autade 30 Nov '16

30 Nov '16

We are configuring 'Count quota' with 'Quota Clone Plugin' Everything is working perfectly when we set limit in quota_rule(quota_rule = *:bytes=500M). In case of unlimited quota(quota_rule = *:bytes=0) - Count quota is updating values * - Quota Clone plugin is not updating values in redis.* We have configured dovecot as mail_plugins = $mail_plugins quota quota_clone mail_log notify mailbox_list_index = yes plugin { quota = count:User quota quota_vsizes = yes quota_rule = *:bytes=0 quota_clone_dict = redis:host=127.0.0.1:port=6379 } -- Sincerely, Prakash P. Autade.

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Dovecot seems to open extra namespaces
by Thorsten Hater 30 Nov '16

30 Nov '16

Dear all, I am slightly confused by the following log entries ...: imap(...): Debug: Namespace inbox: type=private, prefix=INBOX., sep=., inbox=yes, hidden=no, list=yes, subscriptions=yes location=maildir:~/Maildir ...: imap(...): Debug: maildir++: root=~/Maildir, index=, indexpvt=, control=, inbox=~/Maildir, alt= ...: imap(...): Debug: Namespace : type=private, prefix=, sep=, inbox=no, hidden=yes, list=no, subscriptions=no location=fail::LAYOUT=none ...: imap(...): Debug: none: root=, index=, indexpvt=, control=, inbox=, alt= It seems that Dovecot opens two different namespaces, despite only one being configured in 10-mail.conf/15-mailboxes.conf. Is this normal and intended? Further, what is the purpose of the line starting with 'none'? Best regards, Thorsten Dovecot version: 2.2.26.0 on Debian Jessie

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shared/public mailbox application
by Michael Fox 30 Nov '16

30 Nov '16

I'm new to Dovecot and I need help configuring a shared or public mailbox - I'm not sure which is appropriate. I've read the wiki and Peer's book and neither appears to cover what I'd like to do. So I could use some specific help on how to configure a solution for the following: I'd like to create two real mailboxes, let's call them AAA and BBB. Let's call the domain "mydomain". Anyone user can send mail to them, just like any other address: aaa@mydomain or bbb@mydomain. I'd like all IMAP users in mydomain to be able to read the messages in those mailboxes. I'd like all POP users in mydomain to also see those messages. (But I don't think I need help with the virtual part). I'd like only a few designated IMAP users to be able to delete the messages in those mailboxes, including dummy users AAA and BBB themselves. Ideally, I'd like them to appear in the client under a separate namespace from shared mailboxes. Example: INBOX +--- the normal stuff. Shared +--- user1 +--- user2 Special +--- AAA +--- BBB My confusion: 1) I don't know if this requires a shared namespace or a public namespace. It "feels" like it's "public", since all users would have access. But Peer's book and the wiki describe manually creating folders for public namespaces and controlling the contents with manual file manipulation, which leads me to believe that they can't be used for regular mail (although the book and the wiki never say one way or the other). I don't want to manually control files. I want to send mail to the mailbox and delete (see above) it with a client. 2) There are several examples in Peer's book and the wiki, but none seem to match what I want. (This is the problem with documentation that is predominantly example-based). I guess I need more explanation of the mechanical differences between shared and public and why one would pick one over the other. Can someone help? Please be as specific as you can. Thanks much, Michael

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v2.2.27 release candidate released
by Timo Sirainen 30 Nov '16

30 Nov '16

http://dovecot.org/releases/2.2/rc/dovecot-2.2.27.rc1.tar.gz http://dovecot.org/releases/2.2/rc/dovecot-2.2.27.rc1.tar.gz.sig Most interestingly there's a new mail_crypt plugin. It would be nice if crypto gurus could check through it for any issues. Director's tagging fix was also quite a large change, but the new code is already used in production and appears to be working fine. * dovecot.list.index.log rotation sizes/times were changed so that the .log file stays smaller and .log.2 is deleted sooner. + Added mail_crypt plugin that allows encryption of stored emails. See http://wiki2.dovecot.org/Plugins/MailCrypt + stats: Global stats can be sent to Carbon server by setting stats_carbon_server=ip:port + imap/pop3 proxy: If passdb returns proxy_not_trusted, don't send ID/XCLIENT + Added generic hash modifier for %variables: %{<hash algorithm>;rounds=<n>,truncate=<bits>,salt=s>:field} Hash algorithm is any of the supported ones, e.g. md5, sha1, sha256. Also "pkcs5" is supported using SHA256. For example: %{sha256:user} or %{md5;truncate=32:user}. + Added support for SHA3-256 and SHA3-512 hashes. + config: Support DNS wildcards in local_name, e.g. local_name *.example.com { .. } matches anything.example.com, but not multiple.anything.example.com. - Fixed crash in auth process when auth-policy was configured and authentication was aborted/failed without a username set. - director: If two users had different tags but the same hash, the users may have been redirected to the wrong tag's hosts. - Index files may have been thought incorrectly lost, causing "Missing middle file seq=.." to be logged and index rebuild. This happened more easily with IMAP hibernation enabled. - Various fixes to restoring state correctly in un-hibernation. - dovecot.index files were commonly 4 bytes per email too large. This is because 3 bytes per email were being wasted that could have been used for IMAP keywords. - Various fixes to handle dovecot.list.index corruption better. - lib-fts: Fixed assert-crash in address tokenizer with specific input. - Fixed assert-crash in HTML to text parsing with specific input (e.g. for FTS indexing or snippet generation) - doveadm sync -1: Fixed handling mailbox GUID conflicts. - sdbox, mdbox: Perform full index rebuild if corruption is detected inside lib-index, which runs index fsck.

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auth client limit versus service count of mail processes
by Christian Balzer 29 Nov '16

29 Nov '16

Hello, We've got a pretty substantial dovecot installation (versions 2.1.7 and 2.2.13 on the backends, but tested with 2.2.24 as well) and this is the relevant config snippet from 10-master.conf: --- default_process_limit = 1024 default_client_limit = 16384 [...] service imap { # Most of the memory goes to mmap()ing files. You may need to increase this # limit if you have huge mailboxes. #vsz_limit = $default_vsz_limit vsz_limit = 512M # Max. number of IMAP processes (connections) #process_limit = 1024 process_limit = 524288 } service pop3 { # Max. number of POP3 processes (connections) process_limit = 2048 # Reduce spawns from hell service_count = 100 } --- The above works fine, no warnings. Since 2 of our mailbox servers get a high number (2million/day) of IMAP logins and resulting mail process spawns, I pondered doing the service count bit for IMAP as well. But adding a "service_count = 100" line (any value larger than 1 really) to the imap section we get the dreaded: --- Nov 28 17:05:40 mbx09 dovecot: config: Warning: service auth { client_limit=16384} is lower than required under max. load (528384) --- And that's quite true, once reaching that limit auth will pile up and fail eventually. Clearly the pop3 part with a max of 2048 processes (we see about 300 at peak times) neatly fits into the client limit of 16384. Now setting the client limit in the auth section to the required value of course will do no real good in this scenario, as the fd limit becomes the next bottleneck and I'm not going to raise that to 500k, thank you very much. ^o^ So basically my questions here are: 1. Where's the difference in Dovecot's logic between a mail service that has a service count of 1 versus one with >1? 2. Any way to get the process recycling for IMAP going w/o setting the fd limit to a ridiculous amount? Thanks, Christian -- Christian Balzer Network/Systems Engineer chibi(a)gol.com Global OnLine Japan/Rakuten Communications http://www.gol.com/

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what user to use for SIS deduplication?
by Jesus Cea 28 Nov '16

28 Nov '16

Running Dovecot 2.2.25. I have the following line in my root crontab: "/usr/local/bin/doveadm sis deduplicate /home/dovecot/buzones/attachments /home/dovecot/buzones/attachments/queue" This line is execute each hour and the plan is to deduplicate attachments stored in the SIS system. This works well most of the time, but from time to time cron complains with this error: """ Error: mkdir(/home/dovecot/buzones/attachments/bb/f8/hashes) failed: No such file or directory """ In those situations I just create the directory by hand and set the right permissions. Interestingly, most of the time everything works fine, dovecot creates the needed directories and everything is fine. But I get that error every few days and I must create the directory by hand. Am I running the deduplication process correctly?. It is launched as "root" and I would expect it to "setgid()" to the right user/group (dovemail). Should I run it in the dovemail cron?. I have a faint memory of getting the very same error in that case, a missing hash directory, but I am not sure I am recalling correctly. Any advice?. Thanks. -- Jesús Cea Avión _/_/ _/_/_/ _/_/_/ jcea(a)jcea.es - http://www.jcea.es/ _/_/ _/_/ _/_/ _/_/ _/_/ Twitter: @jcea _/_/ _/_/ _/_/_/_/_/ jabber / xmpp:jcea@jabber.org _/_/ _/_/ _/_/ _/_/ _/_/ "Things are not so easy" _/_/ _/_/ _/_/ _/_/ _/_/ _/_/ "My name is Dump, Core Dump" _/_/_/ _/_/_/ _/_/ _/_/ "El amor es poner tu felicidad en la felicidad de otro" - Leibniz

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Problem with multiple ldap passdb
by Martin Wheldon 28 Nov '16

28 Nov '16

Hi mailing list, I'm currently running dovecot 2.2.13 from Debian Jessie, all is running fine. However I am attempting to merge 2 LDAP authentication sources. I would like to attempt to authenticate against the first authentication source, if that fails either by password fail or user not found, then attempt the next LDAP server. I've added the a passdb and userdb entry for the new ldap server. As you can see from the log below the user isn't found in the first LDAP query, but is in the second one. However the authentication fails: Nov 22 13:59:38 he01-imap-01 dovecot: auth: Debug: client in: AUTH#0111#011PLAIN#011service=imap#011secured#011session=WTLjLuRB9QBRlIlQ#011lip=51.254.222.112#011rip=81.148.137.80#011lport=143#011rport=56821#011resp=AG1hcnRpbi53aGVsZG9uQGdyXWVuaGlsbHMtaXQuY28udWsAQ3JhY2spbk4wdw== (previous base64 data may contain sensitive data) Nov 22 13:59:38 he01-imap-01 dovecot: auth: Debug: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<WTLjLuRB9QBRlIlQ>): bind search: base=dc=greenhills-it,dc=co,dc=uk filter=(&(&(ukFirmGhITAccSrvcs=Email)(ukFirmGhITAccLocked=Email-FALSE))(|(uidNumber=martin.wheldon at greenhills-it.co.uk)(mail=martin.wheldon at greenhills-it.co.uk))) Nov 22 13:59:38 he01-imap-01 dovecot: auth: Error: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<WTLjLuRB9QBRlIlQ>): ldap_search(base=dc=greenhills-it,dc=co,dc=uk filter=(&(&(ukFirmGhITAccSrvcs=Email)(ukFirmGhITAccLocked=Email-FALSE))(|(uidNumber=martin.wheldon at greenhills-it.co.uk)(mail=martin.wheldon at greenhills-it.co.uk)))) failed: No such object Nov 22 13:59:38 he01-imap-01 dovecot: auth: Debug: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<WTLjLuRB9QBRlIlQ>): bind search: base=dc=greenhills-it,dc=co,dc=uk filter=(|(uid=martin.wheldon at greenhills-it.co.uk)(mail=martin.wheldon at greenhills-it.co.uk)) Nov 22 13:59:38 he01-imap-01 dovecot: auth: Debug: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<WTLjLuRB9QBRlIlQ>): result: uid=00000001; uid unused Nov 22 13:59:38 he01-imap-01 dovecot: auth: Debug: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<WTLjLuRB9QBRlIlQ>): username changed martin.wheldon at greenhills-it.co.uk -> 00000001 Nov 22 13:59:38 he01-imap-01 dovecot: auth: Debug: ldap(00000001,81.148.137.80,<WTLjLuRB9QBRlIlQ>): result: uid=00000001 Nov 22 13:59:40 he01-imap-01 dovecot: auth: Debug: client passdb out: FAIL#0111#011user=00000001#011temp#011original_user=martin.wheldon at greenhills-it.co.uk I know that the password was entered correctly because if I disable the new ldap config and login I get authenticated properly. Nov 22 14:00:38 he01-imap-01 dovecot: auth: Debug: auth client connected (pid=2626) Nov 22 14:00:39 he01-imap-01 dovecot: auth: Debug: client in: AUTH#0111#011PLAIN#011service=imap#011secured#011session=ipKBMuRBBQBRlIlQ#011lip=51.254.222.112#011rip=81.148.137.80#011lport=143#011rport=38149#011resp=AG1hcnRpbi53aGVsZG9uQGdyXWVuaGlsbHMtaXQuY28udWsAQ3JhY2spbk4wdw== (previous base64 data may contain sensitive data) Nov 22 14:00:39 he01-imap-01 dovecot: auth: Debug: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<ipKBMuRBBQBRlIlQ>): bind search: base=dc=greenhills-it,dc=co,dc=uk filter=(|(uid=martin.wheldon at greenhills-it.co.uk)(mail=martin.wheldon at greenhills-it.co.uk)) Nov 22 14:00:39 he01-imap-01 dovecot: auth: Debug: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<ipKBMuRBBQBRlIlQ>): result: uid=00000001; uid unused Nov 22 14:00:39 he01-imap-01 dovecot: auth: Debug: ldap(martin.wheldon at greenhills-it.co.uk,81.148.137.80,<ipKBMuRBBQBRlIlQ>): username changed martin.wheldon at greenhills-it.co.uk -> 00000001 Nov 22 14:00:39 he01-imap-01 dovecot: auth: Debug: ldap(00000001,81.148.137.80,<ipKBMuRBBQBRlIlQ>): result: uid=00000001 Nov 22 14:00:39 he01-imap-01 dovecot: auth: Debug: client passdb out: OK#0111#011user=00000001#011original_user=martin.wheldon at greenhills-it.co.uk I've done loads of googling and I believe that this is possible so I must either have misread the documentation or am triggering a bug. Neither of which I seem to be able to confirm. Any help would be much appreciated. My broken configuration is below: # 2.2.13: /etc/dovecot/dovecot.conf # OS: Linux 3.16.0-4-amd64 x86_64 Debian 8.6 auth_debug = yes auth_debug_passwords = yes auth_mechanisms = plain login default_vsz_limit = 512 M lmtp_rcpt_check_quota = yes lmtp_save_to_detail_mailbox = yes mail_location = maildir:~/Maildir mail_plugins = " quota" managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave 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-new.conf.ext driver = ldap } passdb { args = /etc/dovecot/dovecot-ldap.conf.ext driver = ldap skip = authenticated } plugin { antispam_backend = pipe antispam_pipe_program = /usr/sbin/sendmail antispam_pipe_program_args = -f;%{auth_user};-r;%{auth_user} antispam_pipe_program_notspam_arg = retrain-as-ham(a)greenhills-it.co.uk antispam_pipe_program_spam_arg = retrain-as-spam(a)greenhills-it.co.uk antispam_spam = Spam antispam_trash = Trash quota = maildir:User quota quota_rule = *:storage=1G quota_rule2 = Trash:ignore quota_rule3 = Spam:ignore sieve = ~/.dovecot.sieve sieve_before = /var/lib/dovecot/sieve/move-spam.sieve sieve_dir = ~/sieve } protocols = " imap lmtp sieve pop3" service imap-login { process_min_avail = 20 service_count = 1 } service imap { process_min_avail = 20 } service lmtp { inet_listener lmtp { address = he01-imap-01.greenhills-it.co.uk 127.0.0.1 port = 2003 } } service pop3 { process_min_avail = 20 } ssl = required ssl_cert = </etc/ssl/certs/combined_2015_greenhills-it.co.uk.cert ssl_cipher_list = ALL:HIGH:!MEDIUM:!LOW:!SSLv2:!EXPORT:!PSK:!DES:!3DES:!MD5:!DES+MD5:!RC4:!SEED+SHA:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA:!eNULL:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_key = </etc/ssl/private/stripped.2015.greenhills-it.co.uk.pem ssl_prefer_server_ciphers = yes ssl_protocols = !SSLv2 !SSLv3 userdb { args = /etc/dovecot/dovecot-ldap-new.conf.ext driver = ldap } userdb { args = /etc/dovecot/dovecot-ldap.conf.ext driver = ldap } protocol lmtp { mail_plugins = " quota sieve" } protocol imap { mail_plugins = " quota imap_quota" } # Working LDAP configuration # /etc/dovecot/dovecot-ldap.conf.ext uris = ldap://he01-auth-01.greenhills-it.co.uk dn = uid=dovecot,ou=people,ou=SRV_Accounts,dc=greenhills-it,dc=co,dc=uk dnpass = VerySecret sasl_bind = no auth_bind = yes ldap_version = 3 base = dc=greenhills-it,dc=co,dc=uk scope = subtree user_attrs = homeDirectory=home,uidNumber=uid,gidNumber=gid,gosaMailQuota=quota_rule=*:storage=%$M user_filter = (|(uid=%u)(mail=%u)(gosaMailAlternateAddress=%u)) pass_attrs = uid=user,userPassword=password pass_filter = (|(uid=%u)(mail=%u)) default_pass_scheme = CRYPT # Non working LDAP configuration # /etc/dovecot/dovecot-ldap-new.conf.ext uris = ldap://dir.greenhills-it.co.uk dn = "cn=dovecot,ou=search accounts,ou=services,dc=greenhills-it,dc=co,dc=uk" dnpass = VerySecret sasl_bind = no tls = yes tls_ca_cert_file = /etc/ssl/certs/GreenhillsCACert.pem tls_require_cert = demand debug_level = -1 auth_bind = yes ldap_version = 3 base = ou=customers,dc=greenhills-it,dc=co,dc=uk scope = subtree user_attrs = homeDirectory=home,uidNumber=uid,gidNumber=gid,ukFirmGhITAccMailQuota=quota_rule=*:storage=%$M user_filter = (&(&(ukFirmGhITAccSrvcs=Email)(ukFirmGhITAccLocked=Email-FALSE))(|(uidNumber=%u)(mail=%u)(ukFirmGhITAccMailAlias=%u))) pass_attrs = uidNumber=user pass_filter = (&(&(ukFirmGhITAccSrvcs=Email)(ukFirmGhITAccLocked=Email-FALSE))(|(uidNumber=%u)(mail=%u))) default_pass_scheme = SSHA Best Regards -- Martin Wheldon Greenhills IT Ltd. Telephone: 01904 238 454 Website: www.greenhills-it.co.uk Greenhills IT Ltd. is a limited company registered in England and Wales. Company Registration No: 06387214 Registered Offices: 2 Greenhills, Claxton, YORK, North Yorkshire, YO60 7SA

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Rebuild UIDs for mdbox
by Darac Marjal 28 Nov '16

28 Nov '16

Hello all, I think I'm hitting an issue with overly large UIDs in one of my mailboxes. I initially thought it was a problem with claws-mail hitting an infinite loop. Claws-mail /seems/ to work fine, until it gets to this one mailbox, wherein the following is logged: [20:23:04] IMAP> 86 SELECT LocalCron [20:23:04] IMAP< * OK [CLOSED] Previous mailbox closed. [20:23:04] IMAP< * FLAGS (\Answered \Flagged \Deleted \Seen \Draft Junk NonJunk) [20:23:04] IMAP< * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft Junk NonJunk \*)] Flags permitted. [20:23:04] IMAP< * 399 EXISTS [20:23:04] IMAP< * 0 RECENT [20:23:04] IMAP< * OK [UNSEEN 399] First unseen. [20:23:04] IMAP< * OK [UIDVALIDITY 1163720154] UIDs valid [20:23:04] IMAP< * OK [UIDNEXT 3069273506] Predicted next UID [20:23:04] IMAP< * OK [HIGHESTMODSEQ 120748] Highest [20:23:04] IMAP< 86 OK [READ-WRITE] Select completed (0.000 + 0.000 secs). imap-thread.c:1344:imap select run - end 0 imap-thread.c:388:generic_cb imap-thread.c:372:found imap 0x22c8f60 imap-thread.c:1431:imap select - end imap.c:3961:select: exists 399 recent 0 expunge 0 uid_validity 1163720154 can_create_flags 1 imap-thread.c:2018:imap fetch_uid - begin imap-thread.c:372:found imap 0x22c8f60 imap-thread.c:372:found imap 0x22c8f60 [20:23:04] IMAP- [fetching UIDs...] [20:23:04] IMAP> 87 UID FETCH 1:* (UID) [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< FETCH (UID 3069273244) [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< TCH (UID 3069273313) [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< TCH (UID 3069273382) [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< TCH (UID 3069273451) [20:23:04] IMAP< [FETCH data - 1024 bytes] [20:23:04] IMAP< [FETCH data - 551 bytes] imap-thread.c:2008:imap fetch_uid run - end 0 imap-thread.c:388:generic_cb imap-thread.c:372:found imap 0x22c8f60 imap-thread.c:2029:imap fetch_uid - end imap.c:542:unlocking session 0x22e4c00 imap.c:4663:get_num_list: got 399 msgs imap.c:4673:removing old messages from /home/darac/.claws-mail/imapcache/mail.darac.org.uk/darac(a)darac.org.uk/LocalCron imap.c:4677:get_num_list - ok - 399 folder.c:2265:Removed message 2147483647 from cache. That last line (Removed message 2147483647 from cache) is repeated ad infinitum. Now, I happened to spot that that number is 2^31 - 1 so started looking to see if claws-mail was handling UIDs incorrectly. That lead me to http://wiki.dovecot.org/Clients/NegativeUIDs. Firstly, that page states that UIDs should be 32-bit integers. If so, why do there appear to be UIDs greater than 3 billion in the mailbox? Secondly, that page gives instructions on how to fix the problem with mbox and maildir backends. However, my mail is stored in mdboxes. Is there a way to re-generate UIDs for mdbox mailboxes? Thanks in advance!

2 2

CPU for Dovecot
by Miloslav Hůla 28 Nov '16

28 Nov '16

Hi, we are planning to change hardware for our standalone Dovecot instance handling ~5800 IMAP users with 1TB mailboxes on local RAID. Is there some recommendation about CPU? We can choose from: - Intel Xeon E5-2620v4 - 2,1GHz@8,0GT 20MB cache, 8core, HT, 85W, LGA2011 - Intel Xeon E5-2623v4 - 2,6GHz@8,0GT 10MB cache, 4core, HT, 85W, LGA2011 The difference is about more cores vs. hi frequency. Thank you, Miloslav

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Dovecot proxy
by Gandalf Corvotempesta 26 Nov '16

26 Nov '16

Hi to all I have some *production* pop3/inappropriate server that i would like to move under a proxy Some questions: 1. Keeping the same original hostname on the proxy (in example mail.mydomain.tld) and changing the hostname on the imap server, makes some troubles like MUA redownloading all the messages? Is dovecot (running on the imap server) happy seeing the hostname change? What about maildirs, where the hostname is wrote on the mail file? 2. Dovecot proxy will proxy the whole pop3/imap traffic or only the login auth? I don't want to expose the mailservers to internet, all imap session must be proxied through the proxy. this because I'll use local IPs on each mail server. 3. Performance for the proxy server? The same as the mailserver or higher due to the missing email computation? In example, the proxy doesn't have to access disks or emails data but has only to transmit what the mailserver osd saying 4. Like question 3, any real users for the proxy? I would like to know some info about hardware and userbase (in example: dual quad xeon 5600, 32Gb ram, 10.000 concurrent sessions) In my case I'm planning for about 100 active sessions. Can i use a small EC2 instance?

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