Reply by email not working (but I'm able to verify each component is working as it should...)

Hello all, I’ve had a good look around this board and haven been unable to find anyone who’s experiencing the same issue as me here. I’m really pulling my hair out at this point.

So, I have:

  • Mail-in-a-Box set up on a VPS
  • Discourse set up on another VPS

Both things are working great. BUT, I just can’t seem to get reply-by-email working.

I’m using POP3 polling, and I can confirm by checking the logs of Discourse and the Mail-in-a-Box logs that Discourse is successfully logging in via POP3. I can also log into the email address on Mail-in-a-Box itself and see the replies by email waiting to be scooped up by Discourse. But what seems to happen is that Discourse authenticates via POP3, doesn’t detect any replies by email, and then logs out.

My reply by email address is set to: reply+%{reply_key}@fiftyshadesof.green

My alternative reply by email addresses are set to: jack+%{reply_key}@fiftyshadesof.green

I have reply@ set up as an alias to jack@, but I’ve noticed in the email headers that the emails might be processed as the latter. Here’s an email header below:

Return-Path: <j****x@****.com>
Delivered-To: jack+583cabd428af27911245150bb3679039@fiftyshadesof.green
Received: from b******h ([127.0.0.1])
    by ********** with LMTP id 8L3WEQDCEmAEsAAAOOEQUQ
    for <jack+583cabd428af27911245150bb3679039@fiftyshadesof.green>; Thu, 28 Jan 2021 13:54:08 +0000
X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on ******
X-Spam-Level:
X-Spam-Status: No, score=0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
    DKIM_VALID_AU,FREEMAIL_FROM,HTML_IMAGE_ONLY_28,HTML_MESSAGE,
    RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE autolearn=no
    autolearn_force=no version=3.4.2
X-Spam-Report:
    * -0.0 RCVD_IN_MSPIKE_H2 RBL: Average reputation (+2)
    * [209.85.222.175 listed in wl.mailspike.net]
    * 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record
    * 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail
    * provider (j****m)
    * 0.7 HTML_IMAGE_ONLY_28 BODY: HTML: images with 2400-2800 bytes of
    * words
    * 0.0 HTML_MESSAGE BODY: HTML included in message
    * 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily
    * valid
    * -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from
    * author's domain
    * -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature
    * -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at
    * https://www.dnswl.org/, no trust
    * [209.85.222.175 listed in list.dnswl.org]
X-Spam-Score: 0.6
Received: from mail-qk1-f175.google.com (mail-qk1-f175.google.com [209.85.222.175])
    (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits))
    (No client certificate requested)
    by ************ (Postfix) with ESMTPS id 10B91A6ACC
    for <reply+583cabd428af27911245150bb3679039@fiftyshadesof.green>; Thu, 28 Jan 2021 13:54:07 +0000 (GMT)
Authentication-Results: ***********; dmarc=pass (p=none dis=none) header.from=****.com
Authentication-Results: ***********;
    dkim=pass (2048-bit key; unprotected) header.d=****.com header.i=@****.com header.b="aU1Sdycv";
    dkim-atps=neutral
Received: by mail-qk1-f175.google.com with SMTP id x81so5267064qkb.0
    for <reply+583cabd428af27911245150bb3679039@fiftyshadesof.green>; Thu, 28 Jan 2021 05:54:07 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
    d=****.com; s=20161025;
    h=mime-version:references:in-reply-to:from:date:message-id:subject:to;
    bh=illVjQUsMQXKmF7F7Mv1ysXAw5aKA0qiK8o4tLS6BMQ=;
    b=aU1SdycvYshTO1kKUFq9r3xR0UJrSOh4Met+wcwqEaK7EWb26bJwbMpa850USAmKjY
    CajKe2iyRobMDtYg9I7zQVKh1i3cqnc8ve1/hSFnEPW/Nc6zapWJn72fdhsPQGyiBASq
    Y5gAIqL6Sz6SaaPAB2i4zcx5I+6jJq/m/mC8o9IxJ3W0YExxQlHc6l+JZR6EqACPccXi
    m53fB9qFCsSU1fmS6VgVE+LegvFozjsMeHjTJ3qzjeHyK82NG3UJSmMzDuyad7yJOBYT
    4wa13+2ERPlRdPASY/dmWQB6+nCQTQhRhXCNMpzUdOFZTPnVdauj+QpcPGQnnvYHl90w
    bBtg==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
    d=1e100.net; s=20161025;
    h=x-gm-message-state:mime-version:references:in-reply-to:from:date
    :message-id:subject:to;
    bh=illVjQUsMQXKmF7F7Mv1ysXAw5aKA0qiK8o4tLS6BMQ=;
    b=udoaf8sLd7IeXLppi0FCOTvqdg8fQkCdLsH4EFwxQSTa9fjax1P1/1yIBexxRHi/zw
    dSpY+/8L/v+VHN9RDw4q9jn3Xx6hqxFzfSLJcEXMoQ6eyVzbCYKNVUNcNPAZ2/hqgqu8
    8XZ5PpYCVUxcsmqSKYcWcbA0JHqGKcJbvTKCugrqeuqByOESSEBzKQS7+xxpFw02yPA4
    1TEyW020NBXVHTVy8eSkGTPpHuK4Q159/ewyXx3aLNDGwCruwXXfh32uO48QA+vsU6m9
    c0oXiGgAdsodj3+dOOmxAiSqa+wlei7xV1YFQ79uorjb+kZXlFu5jGUrVq7BlL3PeB+j
    hn8g==
X-Gm-Message-State: AOAM5332+AyWKnsgCEaYCAgVNKrukhC2+1N032dkVYgN6xcAuJYYTyyQ
    7VWcl/WGEEwNN+BKozjToIRQ+cN836UNAl8TFwDzJpbCOq4=
X-Google-Smtp-Source: ABdhPJwKf65r23SSJmH5DRfIi1VOU4fLExuZ/hO/9EBZMDXrK5m6gYotkBSCDvrI3zTNTumMa6CWFULLQ2eqnIeWDFA=
X-Received: by 2002:a37:4590:: with SMTP id s138mr15675696qka.239.1611842046913;
    Thu, 28 Jan 2021 05:54:06 -0800 (PST)
MIME-Version: 1.0
References: <topic/19@discourse.fiftyshadesof.green>
In-Reply-To: <topic/19@discourse.fiftyshadesof.green>
From: Jack Lenox <j***********.com>
Date: Thu, 28 Jan 2021 13:53:55 +0000
Message-ID: <CAHy8DYjbnLcMHmqSb=-b2B=6ZMxGmba4eT5r0E0j_c4jJfi5Vg@mail.****.com>
Subject: =?UTF-8?Q?Re=3A_=5BFifty_Shades_of_Green_=E2=80=93_Test_Discourse=5D_=5BSamp?=
    =?UTF-8?Q?le_Category=5D_I_wonder_if_I=27ll_be_able_to_reply_to_the_emails?=
    =?UTF-8?Q?_sent_from_this_one?=
To: =?UTF-8?Q?Fifty_Shades_of_Green_=E2=80=93_Test_Discourse?= <reply+583cabd428af27911245150bb3679039@fiftyshadesof.green>
Content-Type: multipart/alternative; boundary="000000000000a3f5e605b9f63853"

I’ve sanitised this slightly for my privacy, but this is just a test box at the moment anyway.

I’ve tried unticking the find related post with key option, but neither is working.

Any help would be greatly appreciated!