I have mailcow with postfix installed on hetzner cloud. I am not system administrator, just developer but I setuped somehow mail server and it seems working. Problem is ,that I dont understand, is that email is sending slow, about 10 seconds. For enduser this is bad experience so I am trying to resolve this. In logs I found this delay


postfix-mailcow_1    | Aug 21 10:21:03 mail postfix/smtps/smtpd[609]: warning: hostname mail......club does not resolve to address 2a01:...::1: Temporary failure in name resolution
postfix-mailcow_1    | Aug 21 10:21:03 mail postfix/smtps/smtpd[609]: connect from unknown[2a01:......:ae58::1]
postfix-mailcow_1    | Aug 21 10:21:03 mail postfix/smtps/smtpd[609]: TLS SNI mail......com from unknown[2a01:.....::1] not matched, using default chain
postfix-mailcow_1    | Aug 21 10:21:03 mail postfix/smtps/smtpd[609]: Anonymous TLS connection established from unknown[2a01:.....8::1]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256
postfix-mailcow_1    | Aug 21 10:21:03 mail postfix/smtps/smtpd[609]: 5F7741C3E28: client=unknown[2a01:.....::1], sasl_method=LOGIN, sasl_username=support@.....com
postfix-mailcow_1    | Aug 21 10:21:03 mail postfix/cleanup[614]: 5F7741C3E28: message-id=<a5b86d0e4f82708f3e5b8bfa6c5e3d60@www.......com>
postfix-mailcow_1    | Aug 21 10:21:11 mail postfix/qmgr[342]: 5F7741C3E28: from=<support@......com>, size=7756, nrcpt=1 (queue active)
postfix-mailcow_1    | Aug 21 10:21:11 mail postfix/smtps/smtpd[609]: disconnect from unknown[2a01.....::1] ehlo=1 auth=1 mail=1 rcpt=1 data=1 quit=1 commands=6
postfix-mailcow_1    | Aug 21 10:21:11 mail postfix/smtp[615]: 5F7741C3E28: replace: header Received: from www........com (unknown [IPv6:.....:ae: Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 5F7741C3E28??for <etet@yopmail.com>; Fri, 21 Aug 2020 10:21:03 +0200 (CEST)
postfix-mailcow_1    | Aug 21 10:21:11 mail postfix/smtp[615]: 5F7741C3E28: to=<etet@yopmail.com>, relay=smtp.yopmail.com[87.....155]:25, delay=8.5, delays=8.2/0.04/0.16/0.09, dsn=2.0.0, status=sent (250 mail saved)
postfix-mailcow_1    | Aug 21 10:21:11 mail postfix/qmgr[342]: 5F7741C3E28: removed

so from 03 seconds to 11 seconds some waiting or I dont know what. Can someone please suggest what can I do?

14 days later

Hello @sercul ,
We have exactly the same problem, we are also on Hetzner, and installed Mailcow one week ago.
Everything works fine, but sending mail is really slow as you, 10 ~ 20 seconds under Thunderbird, but this works correctly after.
And strange behaviour on K9-Mail Android, the SMTP configuration is rejected, I suppose the test inside K9 is too long and consider something wrong to accept the configuration (exactly the same as on thunderbird…)

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  • diekuh

    • Community Hero
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    Moolevel 110
  • Post #3

Check your rspamd-mailcow logs.

And don’t use port 25, @lakano

I don’t use port 25 @diekuh , but I have may be found the problem, it’s seems to be caused by the IPv6 reverse DNS.
I’ve just updated the reverse DNS, I don’t known how many hours I need to wait, but I keep you on touch

Problem solved for me.
@sercul check your reverse DNS is set for IPv6 for your « ::1 », « ::0 » and « :: » IPv6 address (the right part in Hetzner)
Then, check in your DNS you’ve correctly set your @ AAAA to your full IPv6 finishing per « ::1 »
Look at your ACME logs, and check one hour later that you’re cert for IPv6 is correctly verified.

3 years later

Hi. I am trying to solved the delay as well and having trouble finding reverse dns for ip6 config options on the Hetzner Robot. Would you point me to it ?

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