Hi @all

First of all, thanks for this great mailcow dockerized project!
I have the problem that sending mails by SMTP takes a very long time.

I found several threads regarding the same problem but no solution for my problem.

  • I’m connecting via SMTP on port 465 SSL/TLS (so not Port 25 to avoid this problem)
  • IPv6 is not enabled and I have no public IPv6 address, so I have no AAAA record for my mail server and the PTR record is only set for the IPv4 address
  • Sending mails is always slow independent of using
    • SoGo
    • Thunderbird on my client PC
    • GMail App on Android
    • Server in our company running a CRM and sending mails using PHP (here there’s sometimes even a timeout while sending)

Here’s the postfix log. This is recorded while sending an email using Thunderbird.
It shows a delay of approx. 7sec before processing the email further…

16.08.2021, 08:56:27 info C164F343F7: removed
16.08.2021, 08:56:27 info C164F343F7: to=<receivermail@gmail.com>, relay=gmail-smtp-in.l.google.com[74.125.140.27]:25, delay=13, delays=11/0.02/1.2/0.45, dsn=2.0.0, status=sent (250 2.0.0 OK 1629096987 3si10838896wry.379 - gsmtp)
16.08.2021, 08:56:26 info Trusted TLS connection established to gmail-smtp-in.l.google.com[74.125.140.27]:25: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-256) server-digest SHA256
16.08.2021, 08:56:26 info connect to gmail-smtp-in.l.google.com[2a00:1450:400c:c08::1b]:25: Network is unreachable
16.08.2021, 08:56:25 info disconnect from mail.my.tld[1.2.3.4] ehlo=1 auth=1 mail=1 rcpt=1 data=1 quit=1 commands=6
16.08.2021, 08:56:25 info C164F343F7: from=<sender@my.tld>, size=3732, nrcpt=1 (queue active)
16.08.2021, 08:56:18 info C164F343F7: message-id=<644e4cb4-e5f4-7349-c21c-a932b599211e@my.tld>
16.08.2021, 08:56:18 info C164F343F7: replace: header Received: from [172.21.0.36] (mail.my.tld [1.2.3.4])??(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)?? key-exchange X25519 server-signature RSA-PSS (2048 bits))??(No client cer from mail.my.tld[1.2.3.4]; from=<sender@my.tld> to=<receivermail@gmail.com> proto=ESMTP helo=<[172.21.0.36]>: Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id C164F343F7??for <receivermail@gmail.com>; Mon, 16 Aug 2021 08:56:14 +0200 (CEST)
16.08.2021, 08:56:18 info C164F343F7: client=mail.my.tld[1.2.3.4], sasl_method=PLAIN, sasl_username=sender@my.tld
16.08.2021, 08:56:14 info Anonymous TLS connection established from mail.my.tld[1.2.3.4]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)
16.08.2021, 08:56:14 info connect from mail.my.tld[1.2.3.4]
16.08.2021, 08:56:03 info statistics: max cache size 1 at Aug 16 08:52:37

Any help is greatly appreciated.

Best regards
Bastian

    2 years later

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    9 months later

    I have the same problem, even though I just updated mailcow to latest version. How can this be fixed?! Obviously the problem is still there. I have a client with a webshop, when an order is made, an email is sent (not queued) and the UI is waiting for the email to be sent… indefinitely. The buyers who made a purchase are all waiting for the confirmation emails to be dispatched and it sometimes times out.. This must be fixed!

    From my understanding this is intentional. It’s part of the email servers security machanism to accept incoming sending requests only after some time. If you send another email right after the first one this will be sent much quicker. 8 seconds vs 2 seconds waiting time. I have also noticed this behavior with email sending platforms, hence i dont think there is a fix, its normal behavior for an email server.
    The way to avoid the problem is to tell the sending application not to wait for confirmation from the email server that the email got sent. Then the UI would just move on, the client sees the order is accepted and by that time the email should get through as well.

    I guess you are talking about the greylisting feature of rspamd. Rspamd - rapid spam filtering system. Icon Greylisting module

    Rspamd - rapid spam filtering system. Icon Rspamd - rapid spam filtering system.
    Greylisting module
    Rspamd is an advanced spam filtering system and email processing framework that allows evaluation of messages by a number of rules including regular expressions, statistical analysis and custom services such as URL black lists.

    You could turn that off (but receive more SPAM mails then):

    docs.mailcow.email Icon Disable Greylisting - mailcow: dockerized documentation

    docs.mailcow.email Icon docs.mailcow.email
    Disable Greylisting - mailcow: dockerized documentation
    None
    docs.mailcow.email

    Or you could whitelist your web shop’s sending IP address:

    docs.mailcow.email Icon Blacklist / Whitelist - mailcow: dockerized documentation

    docs.mailcow.email Icon docs.mailcow.email
    Blacklist / Whitelist - mailcow: dockerized documentation
    None
    docs.mailcow.email

    I’m not sure it has to do with rspamd. It’s not about revieceing emails, its about a delay in sending emails.

    1) The webshop sends an order confirmation to the customer.
    2) The Server recieves this request but waits
    3) 8-10s pass without anthing happen - the webshop waits for sending confirmation
    4) Email gets sent out from the server to the customer.
    5) Webshop shows send confirmation message, “thanks for purchase, we sent you an email”

    So what we try to elimitate is No 3). This waiting time where nothing happens.

      reventor So if I understand your case you are using mailcow as the mail relay server for your webshop? Did you try whitelisting it in mailcow? Or configure authentication for SMTP in your web shop system?

        See this thread, the same problem:
        mailcow community Icon smtp transaction delay are slowing down post on my forums

        mailcow community Icon mailcow communityDiscussion
        smtp transaction delay are slowing down post on my forums
        Author avatar image HA-TB303
        I am having somewhat of a discussion with the developers/support engineers of the forums software I use. I am experiencing slow POST when someone replies to a message on my forums. After searching for days, it turns out, when someone replies to a forum post, the forums software waits for the topic
        mailcow community
        10 2

        Please add the webshop IP address to the postscreen filter:
        docs.mailcow.email Icon Whitelist IP in Postscreen - mailcow: dockerized documentation

        docs.mailcow.email Icon docs.mailcow.email
        Whitelist IP in Postscreen - mailcow: dockerized documentation
        None
        docs.mailcow.email

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