From 88f18f9a0c8618915ab90ec9db8ca5bcb2b7a521 Mon Sep 17 00:00:00 2001 From: darksun Date: Mon, 24 Dec 2018 19:18:45 +0800 Subject: [PATCH] =?UTF-8?q?=E9=80=89=E9=A2=98:=20How=20to=20detect=20autom?= =?UTF-8?q?atically=20generated=20emails?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...o detect automatically generated emails.md | 144 ++++++++++++++++++ 1 file changed, 144 insertions(+) create mode 100644 sources/tech/20181222 How to detect automatically generated emails.md diff --git a/sources/tech/20181222 How to detect automatically generated emails.md b/sources/tech/20181222 How to detect automatically generated emails.md new file mode 100644 index 0000000000..23b509a77b --- /dev/null +++ b/sources/tech/20181222 How to detect automatically generated emails.md @@ -0,0 +1,144 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (How to detect automatically generated emails) +[#]: via: (https://arp242.net/weblog/autoreply.html) +[#]: author: (Martin Tournoij https://arp242.net/) + +How to detect automatically generated emails +====== + +### How to detect automatically generated emails + + +When you send out an auto-reply from an email system you want to take care to not send replies to automatically generated emails. At best, you will get a useless delivery failure. At words, you will get an infinite email loop and a world of chaos. + +Turns out that reliably detecting automatically generated emails is not always easy. Here are my observations based on writing a detector for this and scanning about 100,000 emails with it (extensive personal archive and company archive). + +### Auto-submitted header + +Defined in [RFC 3834][1]. + +This is the ‘official’ standard way to indicate your message is an auto-reply. You should **not** send a reply if `Auto-Submitted` is present and has a value other than `no`. + +### X-Auto-Response-Suppress header + +Defined [by Microsoft][2] + +This header is used by Microsoft Exchange, Outlook, and perhaps some other products. Many newsletters and such also set this. You should **not** send a reply if `X-Auto-Response-Suppress` contains `DR` (“Suppress delivery reports”), `AutoReply` (“Suppress auto-reply messages other than OOF notifications”), or `All`. + +### List-Id and List-Unsubscribe headers + +Defined in [RFC 2919][3] + +You usually don’t want to send auto-replies to mailing lists or news letters. Pretty much all mail lists and most newsletters set at least one of these headers. You should **not** send a reply if either of these headers is present. The value is unimportant. + +### Feedback-ID header + +Defined [by Google][4]. + +Gmail uses this header to identify mail newsletters, and uses it to generate statistics/reports for owners of those newsletters. You should **not** send a reply if this headers is present; the value is unimportant. + +### Non-standard ways + +The above methods are well-defined and clear (even though some are non-standard). Unfortunately some email systems do not use any of them :-( Here are some additional measures. + +#### Precedence header + +Not really defined anywhere, mentioned in [RFC 2076][5] where its use is discouraged (but this header is commonly encountered). + +Note that checking for the existence of this field is not recommended, as some ails use `normal` and some other (obscure) values (this is not very common though). + +My recommendation is to **not** send a reply if the value case-insensitively matches `bulk`, `auto_reply`, or `list`. + +#### Other obscure headers + +A collection of other (somewhat obscure) headers I’ve encountered. I would recommend **not** sending an auto-reply if one of these is set. Most mails also set one of the above headers, but some don’t (but it’s not very common). + + * `X-MSFBL`; can’t really find a definition (Microsoft header?), but I only have auto-generated mails with this header. + + * `X-Loop`; not really defined anywhere, and somewhat rare, but sometimes it’s set. It’s most often set to the address that should not get emails, but `X-Loop: yes` is also encountered. + + * `X-Autoreply`; fairly rare, and always seems to have a value of `yes`. + + + + +#### Email address + +Check if the `From` or `Reply-To` headers contains `noreply`, `no-reply`, or `no_reply` (regex: `^no.?reply@`). + +#### HTML only + +If an email only has a HTML part, but no text part it’s a good indication this is an auto-generated mail or newsletter. Pretty much all mail clients also set a text part. + +#### Delivery failures + +Many delivery failure messages don’t really indicate that they’re failures. Some ways to check this: + + * `From` contains `mailer-daemon` or `Mail Delivery Subsystem` + + + +Many mail libraries leave some sort of footprint, and most regular mail clients override this with their own data. Checking for this seems to work fairly well. + + * `X-Mailer: Microsoft CDO for Windows 2000` – Set by some MS software; I can only find it on autogenerated mails. Yes, it’s still used in 2015. + + * `Message-ID` header contains `.JavaMail.` – I’ve found a few (5 on 50k) regular messages with this, but not many; the vast majority (thousends) of messages are news-letters, order confirmations, etc. + + * `^X-Mailer` starts with `PHP`. This should catch both `X-Mailer: PHP/5.5.0` and `X-Mailer: PHPmailer blah blah`. The same as `JavaMail` applies. + + * `X-Library` presence; only [Indy][6] seems to set this. + + * `X-Mailer` starts with `wdcollect`. Set by some Plesk mails. + + * `X-Mailer` starts with `MIME-tools`. + + + + +### Final precaution: limit the number of replies + +Even when following all of the above advice, you may still encounter an email program that will slip through. This can very dangerous, as email systems that simply `IF email THEN send_email` have the potential to cause infinite email loops. + +For this reason, I recommend keeping track of which emails you’ve sent an autoreply to and rate limiting this to at most n emails in n minutes. This will break the back-and-forth chain. + +We use one email per five minutes, but something less strict will probably also work well. + +### What you need to set on your auto-response + +The specifics for this will vary depending on what sort of mails you’re sending. This is what we use for auto-reply mails: + +``` +Auto-Submitted: auto-replied +X-Auto-Response-Suppress: All +Precedence: auto_reply +``` + +### Feedback + +You can mail me at [martin@arp242.net][7] or [create a GitHub issue][8] for feedback, questions, etc. + +-------------------------------------------------------------------------------- + +via: https://arp242.net/weblog/autoreply.html + +作者：[Martin Tournoij][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://arp242.net/ +[b]: https://github.com/lujun9972 +[1]: http://tools.ietf.org/html/rfc3834 +[2]: https://msdn.microsoft.com/en-us/library/ee219609(v=EXCHG.80).aspx +[3]: https://tools.ietf.org/html/rfc2919) +[4]: https://support.google.com/mail/answer/6254652?hl=en +[5]: http://www.faqs.org/rfcs/rfc2076.html +[6]: http://www.indyproject.org/index.en.aspx +[7]: mailto:martin@arp242.net +[8]: https://github.com/Carpetsmoker/arp242.net/issues/new