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How Close.io (YC W11) built per-recipient email tracking (close.io)
22 points by anemitz 1547 days ago | hide | past | web | 24 comments | favorite



> we can send unique message content to each recipient of an email while still having recipients believe they are receiving the same message

So you know that people don't like receiving personalized messages that are tracked and yet you are proud that you have devised a way to shovel them down their throats anyways. Good stuff.

(edit) I would've not minded if this were purely technical post on how you set things up, but the way its edited at the moment just reeks of disrespect towards those on a receiving end of your emails.


The emails would be personalized and tracked regardless, all that this does is improve the tracking by identifying which recipient opened the message instead of a more general "email was opened" tracking event. It's not exactly trickery, just creative use of SMTP commands. Also, it still relies on a tracking pixel, which as usual won't work if the recipient has images disabled in their email client.


"which recipient opened the message" and: The times they opened it, where they were when they opened it, and what operating system and user agents they were using when they opened it.


All of those things are possible with any simple tracking pixel anyway. The only difference here is being able to distinguish specific recipients from a multi-recipient email.


If you visit a website and that website gleans this information about you, that is one thing.

If you simply receive an email and read it, and the sender can glean the same information, that is something entirely different.


Tracking pixels in emails have been around for many years and are used by almost everybody. That's why many email clients block images by default.


That is not an argument for doing it. As I wrote sarcastically in the other thread on this page:

  "Oh, but everyone does it, so it's ok right?"


This is really in poor taste. Can you imagine if the email to Bob said "hey lets meet at the pub at 6" and the email to Alice said "hey lets meet at the pub at 4".

I know this is unlikely, but sending an email that looks like each party is getting the same thing but in fact are getting different emails just is bad.

The tracking thing is not a big deal, seems like everyone does it. Just block images and you are golden.


Author here.

You're entirely correct that this part of the SMTP spec does potentially allow for dubious behavior -- and that's one of the reasons I wanted to publish this article. I have a feeling this is one of the little-known secrets of email sending which we should all be aware of.

EDIT: Also, I'd like to point one that the real textual content of a message can't differ when sending through Close.io so the scenario you explained above isn't possible within our app.


Ignoring the terminology errors, and the fact that this is a pretty scummy and uninteresting business model (it's kind of like blogging about the awesome architecture you built to predict when people will be at home eating dinner so you can robocall them with telemarketing crap right then), this kind of system is also inherently unreliable.

None of my email clients, on OS X, Windows, or Linux, will show that pixel unless I press a button or take some action.

And I believe that is increasingly the default behavior of email clients, isn't it? Which means this technique will increasingly not work, and there is nothing close.io can do about it.


The internet is fun, so I'll bite.

> scummy and uninteresting business model

We make a sales communicate platform that integrates CRM + calling + email. <sarcasm> You're right, it is a pretty uninteresting business model in that we don't use some new-fangled financial instruments to cook our books -- it's just boring ole' monthly recurring revenue at a SaaS company. </sarcasm>

Scummy? Don't even know where to begin on that one -- but if you're in the Bay Area ping me. I'd be happy to sit down and entertain any ideas you may have that we run a scummy outfit. Seriously. I really would like to understand the context behind that statement. It's not something I take lightly as a founder.

> None of my email clients, on OS X, Windows, or Linux, will show that pixel unless I press a button or take some action.

Yes and no. You can set most clients to load images by default -- I haven't tested the default settings on all clients so I can't speak about what percentage that accounts for. I'd assume someone like Mailchimp/Marketo/Pardot/etc. may have published some interesting findings about this.

You're entirely right, however -- we can't do anything if a client blocks images. And that's OK. Tracking is a feature our customers love being able to utilize when they can, but they also understand that it's not entirely accurate.


By "scummy" I am talking about the same thing as the other people in this thread talking about "poor taste", "ethics", and "morality".

Surreptitiously tracking users without their knowledge or consent (and I mean the end users, not your users who are paying you to do it) just isn't something cool to brag about, any more than robocalling people at dinner, or a thousand other things that are nevertheless legal and make monthly recurring revenue for those who do them.

Not saying you shouldn't be able to do it; a lot of unseemly and faintly repulsive things happen in the name of marketing. I'm just saying it's kind of a lame thing to do in general, and it is pretty off-putting to read a blog post that basically says, "Look how rad we are for tricking all these people and tracking them without their knowledge!"


"How Close.io (YC W11) exploited a technical loop hole in the way email and the web works in order to mine data about users without their knowledge or permission"

Oh, but everyone does it, so it's ok right?


I don't get the "without their knowledge or permission" part. That could go for anyone who puts a tracking pixel into an email. It doesn't apply specifically to the "technical loophole" discussed in this article. I'm not a fan of tracking pixels either, but this isn't really the point of the article.


Yes, that can and does go for anyone who puts a tracking pixel into an email.

And to address the: 'I don't get the "without their knowledge or permission" part.' - What don't you get about this? The recipient doesn't realise the tracking is taking place, and the sender never asked permission to perform the tracking, nor to store the data...


I'm saying that the question of (lack of) permission is a different topic from the specific SMTP technique described in the article. The SMTP technique doesn't change anything with respect to privacy compared to standard tracking pixels. The assumption going into the article was that tracking pixels are already being used.

> the sender never asked permission to perform the tracking, nor to store the data

Well, in this case the sender would be someone using Close.io as their CRM. So they actually almost certainly do want this tracking to be performed.


The authors use of SMTP and IMAP is confusing. This is a standard tracking pixel, performed in the same way that everybody else does it. There is nothing new here.

SMTP and IMAP are transport protocols. For transporting text around:

"By utilizing SMTPs RCPT TO command" - He's not utilising anything special. This is exactly how every other email that employs tracking pixels is sent. A separate recipient and message body for each recipient.

"Remove any messages stored by the SMTP server" ... "Google's SMTP servers store a copy of every message"

Nope. SMTP is used for mail servers to pass email about. An SMTP server doesn't store mail, apart from in it's temporary queue before forwarding it on.

"Store sent mail in IMAP" ... "If using a service like Gmail which stores all sent messages automatically in IMAP" - Again, you don't store email in a message transfer protocol.

This article reads particularly badly because of the repeated incorrect use of terminology.

[edit] And to address your comment, "they actually almost certainly do want this tracking to be performed" - "want" is an interesting word to use there. If there was a tick box in the top right corner of peoples email clients which said:

  Allow senders to track when you open a message,
  where you were when you opened it, and various
  pieces of information about your system
99% of people would untick that box.


Incorrect terminology should now be fixed. Thanks for calling that out.

Note that Google's SMTP servers do store the messages in your sent mail folder. I don't claim to know exactly how they do this (IMAP, direct access to filesystems, whatever), but the messages are stored -- and yes, obviously the SMTP protocol doesn't facilitate this but their SMTP servers perform this action.


I said "want" in the context of the _sender_ not the recipient. Ie. the person who is using Close.io to send a sales email to a recipient. In this case, the _sender_ would want to know if the email was opened or not.


When you send an email with Gmail's SMTP servers, Gmail automatically stores a copy of that message in your "sent" IMAP folder. This is what the author was talking about.


Not "in your sent IMAP folder" ... "in your sent folder, which can be accessed via IMAP"


I hate social sharing buttons and ad networks just as much as the next guy, so I completely understand where you're coming from with this comment. However, you have the option to completely opt-out of any kind of email tracking by always reading only the text portion of emails sent to you.

Asking whether this is morally/ethically OK is probably not the right question. As we've seen with any technology, if something is possible to track/store/analyze it will be. If tracking email opens (or any data on the internet) is not something we want to accept as a society we need to find ways to ensure tracking those actions under any circumstances is impossible -- not just leave it up to chance.


I agree. I am the author of https://emailprivacytester.com/

  "morally/ethically OK is probably not the right question"
It is always the right topic to bring up, whenever anybody nonchalently states that they are doing it and are proud about it. Perhaps the author hadn't considered the morality of what he does. Perhaps somebody else reading this hadn't either.


So, if I understand correctly, I can test if someone received a specific email just by testing the tracking link with known email addresses? Fun!




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