From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC9EA3DB87; Tue, 9 Jan 2024 21:47:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ck7qHMbe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49FD1C433F1; Tue, 9 Jan 2024 21:47:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1704836843; bh=TSDpF1S8lQAwZw/lVeytxTPjeCJbcaeqA8hGl4RvNpg=; h=Date:From:To:Subject:From; b=ck7qHMbeWEPqkpBp13uskAiTzYpWH/CJLZ46IaJ9z/DAtmO+w1hxLADCQ7yA5Z8mp uNpXF/bfFdNwxwkad8Ij+UsKyDneA4BdA6NP0dOY5zGeB823DtItPAVXX3tXvluWz3 uyG/4PpKT4TnDSaI1Nr0e+ykw6AexMClbfA9nPRI= Date: Tue, 9 Jan 2024 16:47:22 -0500 From: Konstantin Ryabitsev To: robh@kernel.org, users@linux.kernel.org, workflows@vger.kernel.org Subject: PSA: nullmailer should be avoided Message-ID: <20240109-alluring-fanatic-manul-cfa5d2@lemur> Precedence: bulk X-Mailing-List: workflows@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Hi, all: I know some of you use nullmailer for sending outgoing mail, but it *really* must be avoided, as the messages it sends are not RFC-2822 compliant. Per that RFC, header lines MUST NOT be longer than 998 characters in length, which is not something nullmailer appears to be paying any attention to. Some mailservers will outright reject messages with lines exceeding 998 characters (Exim), and some will force-insert at exactly character 998, regardless of what that does to the header: https://lore.kernel.org/linux-kernel/20240109171807.GA2783042-robh@kernel.org/raw You will notice, that the enforced line-break cuts across the email address: Cc: [...] Sergey Shtylyov A message with such header *may* get delivered, or it may get rejected due to malformed headers (e.g. Exim does that by default). Anyone then attempting to reply to such message will likely have trouble as well. Unfortunately, nullmailer appears to always re-parse To/Cc headers, so even if the original email properly wrapped the recipients headers before it was fed to nullmailer, everything will then just be concatenated into one long line: https://github.com/bruceg/nullmailer/blob/master/src/inject.cc#L384 I'll open an issue with nullmailer about this, but the project doesn't appear very alive, so your best bet is to switch to msmtp. It has msmtp-{enqueue,listqueue,runqueue} commands that will do everything nullmailer can do and won't break your mail. -K