Through our platform I'm sending automatic emails with an unsubscribe link.
The unsubscribe has the following format:
http://example.com/unsubscribe?id={id}&c={code}
The Id represents the UserId in the database, the Code is just some hash that is linked to the User (so people can't unsubscribe random people).
Problem is that I'm getting exceptions that the UserId does not match the database (about 5-10%) - the Id is just way larger then the largest Id in our database.
Another weird thing is that the query parameters seem to be reversed. It is suddenly ?c={code}&id={id} instead of ?id={id}&c={code}.
The code is really really simple, and I can't believe there is anything that can go wrong in constructing the original message. In a way there don't seem to be any other code paths.
I can come up with two possible causes:
Some email tools mangle the url as some kind of anti spam / phishing / tracking / footprinting?
This is somehow related to character encoding going bad or something similar?
But in a way I have no clue and I'm really at a loss here. I really would like to fix this, because the last thing I want to do is spam people by accident that can't unsubscribe.
Can anyone point me in the right direction?
Related
Over the past few months random email addresses, some of which are on known spam lists, have been added at the rate of 2 or 3 a day to my website.
I know they aren't real humans - for a start the website is in a very narrow geographical area, and many of these emails are clearly from a different country, others are info# addresses that appear to have been harvested from a website, rather than something a human would use to sign up to a site.
What I can't work out is, what are reasons for somebody doing this? I can't see any benefit to an external party beyond being vaguely destructive. (I don't want to link to the site here, it's just a textbox where you enter email and press join).
These emails are never verified - my question isn't about how to prevent this, but what are some valid reasons why somebody might do this. I think it's important to understand why malicious users do what they do.
This is probably a list bombing attack, which is definitely not valid. The only valid use I can think of is for security research, and that's a corner case.
List bomb
I suspect this is part of a list bombing attack, which is when somebody uses a tool or service to maliciously sign up a victim for as much junk email as possible. I work in anti-spam and have seen victims' perspectives on this: it's nearly all opt-in verifications, meaning the damage is only one per service. It sounds like you're in the Confirmed Opt-In (COI) camp, so congratulations, it could be worse.
We don't have good solutions for list bombing. There are too many problems to entertain a global database of hashed emails that have recently opted into lists (so list maintainers could look up an address, conclude it's being bombed, and refuse to invite). A global database of hashed emails opting out of bulk mail (like the US Do Not Call list or the now-defunct Blue Frog's Do Not Intrude registry but without the controversial DDoS-the-spammers portion) could theoretically work in this capacity, though there'd still be a lot of hurdles to clear.
At the moment, the best thing you can do is to rate-limit (which this attacker is savvy enough to avoid) and use captchas. You can measure your success based on the click rate of the links in your COI emails; if it's still low, you still have a problem.
In your particular case, asking the user to identify a region via drop-down, with no default, may give you an easy way to reject subscriptions or trigger more complex captchas.
If you're interested in a more research-driven approach, you could try to fingerprint the subscription requests and see if you can identify the tool (if it's client-run, and I believe most are) or the service (if it's cloud-run, in which case you can hopefully just blacklist a few CIDR ranges instead). Pay attention to requesters' HTTP headers, especially the referer. Browser fingerprinting it its own arms race; take a gander at the EFF's Panopticlick or Brian Kreb's piece on AntiDetect.
Security research
The only valid case I can consider, whose validity is debatable, is that of security research (which is my field). When I'm given a possible phishing link, I'm going to anonymize it. This means I'll enter fake data rather than reveal my source. I'd never intentionally go after a subscription mechanism (at least with an email I don't control), but I suppose automation could accidentally stumble into such a thing.
You can avoid that by requiring POST requests to subscribe. No (well-designed) subscription mechanism should accept GET requests or action links without parameters (though there are plenty that do). No (well-designed) web crawler, for search or archiving or security, should generate POST requests, at least without several controls to ensure it's acceptable (such as already concluding that it's a bad actor's site). I'm going to be generous and not call out any security vendors that I know do this.
I've always assumed that it's risky to identify users in urls within emails. For example, let's say my app is something like eventBrite. I'm inviting a set of users to an upcoming event. I create unique urls for each user's email which allows them to simply click those url's in the email to accept or decline. Ie, they will not have to authenticate with the website.
If they view the email on a mobile device or a public computer through webmail, then clicking the links will fully accept/decline.
Is this approach too risky? I had assumed you should avoid this as something could see those urls and make requests on them which would trigger false accepts/declines.
It'a an opinion but I would assume the link itself can be more secure than the email actually. You can make the accept link valid only through certain period of time (it would not make much sense otherwise anyways).
Moreover, you can make it pretty much arbitrary long. So it's basically arbitrarily hard to guess.
That would leave two options to "see" the link, that I can think of. Physically seeing it by eaves dropping. But you could generate a mail in the html form, which would allow you to hide the full link behind a hyper-ref text. Like Accept / Decline.
There are several parts to this answer:
Is it secure? Absolutely not. It's security through obscurity. You're betting somebody can't guess the link which, as long as it's a finite string then they totally can and as soon as they do, they can RSVP to your event.
Follow up Does it matter? Probably not. I imagine the chances of somebody trying to spoof an RSVP to an event are pretty slim. I absolutely wouldn't protect anything critical this way but if you're just doing something like event RSVP etc (no money changing hands) I don't see anything wrong with this approach. As luk32 said, you can also make the links valid for limited amounts of time etc.
The real issue here, (unless there's something you're not telling us and this is somehow a high value target) is how likely is somebody to accidentally stumble on one of these links and RSVP to an event they aren't going to? You can make the chances of that exceedingly unlikely by generating the links in a sufficiently random manner so that no two links are a like. In this case, I don't think security is the big concern so much as data integrity. That is, is the data you're receiving valid.
The title being self explanatory, i would like to add some points to it.
1.Firstly, is it possible to track all these (READ,DELETED,SOFT BOUNCE,HARD BOUNCE) without using third party API?
2. If no, which third party services provide you the same ?
I am aware about the <img src="send-identifiers-to-this-url-to-track"/>, but this can only get me "No.of Reads/Forwards", but not deleted.
Anybody in for help ?
There are a number of things you can detect with your own software and no third party, though I don't know how they map onto the categories you list:
Tracking images and links, like you said (READ).
No mail server to take the message, e.g There might not be any MX record for the domain or your mailserver IP might be blocked by DNSBL (maybe what you mean by HARD BOUNCE?)
Mail server response codes. This might tell you for example:
Your email was rejected because the mailbox was over capacity etc (probably SOFT BOUNCE)
Rejected because it's spam (probably HARD BOUNCE)
Greylisted or something (probably SOFT BOUNCE)
There is basically nothing you can to detect the difference between unread and deleted messages though. That is also true of third party services. You will not even detect read messages unless your recipient turns on tracking images or clicks on a tracking link.
It's pretty hard to get this information, for instance I had to implement a postfix log analyzer that is mining the bounce information (soft/hard) and the reason why they occured and make it available via API in a structured form.
I got a request from my client that they want to add stars (★) to their email subject (They send these mails through the application we made as a part of bigger CRM for them).
I tried to send a test mail, and the email title is displayed nicely in my Gmail account, and I must agree with my client that it is eye catching, but what came to my mind is that this may be a spam magnet, so I googled about it but I can't find the actual "don't do this".
Generaly, my oppinion would be not to use it, but now I have to explain to the client why. My best explanation whould be there is a probability your emails will be treated as spam but I don't have the background for this statement.
Do you have any suggestions about what should I do?
The only information I could find is on the SpamAssassin page of how to avoid false positives. The only relevant part I found was this part.
Do not use "cute" spellings, Don't S.P.A.C.E out your words, don't put
str#nge |etters 0r characters into your emails.
SpamAssassin is a very widely used spam filtering tool. However, simply breaking one of the rules (strange characters) alone wouldn't get an email marked as spam. But combined with some other problems could lead to your email being considered spam. That being said, if your email is a completely legitimate business email, it's likely that few other rules are triggered, and using the special characters wouldn't create a huge problem. That being said, you should probably try out a couple test emails on SpamAssassin and a couple other spam filtering tools in order to come to a better conclusion on the emails you plan to send out.
Simply explain to your client as you have explained to SO: you stated that the star made it eye catching: this doesn't directly mean that it will be treated as spam, but you could explain how that concept COULD be considered spam.
If the star is part of their branding, however, this could be quite a nice way in which your client expresses themselves.
Spam emails are becoming more and more like what one would consider 'normal', so I think they have trial it internally, test the concept.
Talk it over with your client - there is going to be no basis in hard fact with things like this, purely social perception.
More and more retailers are using unicode symbols in their subject lines since a few months. Of course it's in order to gain more attention in cluttered inboxes. Until now, there has been absolutely no evidence that such symbols increase the likelihood of failing spam filter tests. However, keep in mind that rare symbols might not render (correctly) across all mail user agents. Especially keep an eye on Android and Blackberry smartphones, but also on Outlook. In addition, due to a Hotmail bug symbols will render much bigger in subect lines and in the email body within the web front end. In fact, they are beeing replaced by images. All in all, the star shouldn't make any problems. At least, if it's encoded correctly in the subject line. So, go for it.
Does anyone know a good tool to test whether your emails are going into spam folders?
My web app generates emails to users, and I've been getting a lot of reports back from people saying "hey, no one ever responded to my message".
I have SPF rules in place and functioning correctly (email header shows an spf pass). I've also run my message through spam assassin and it scores very low.
Any other ideas?
To know if your email goes in the inbox, you need to get a metric called "Inbox Placement Rate". This indicator can be provided by Return Path, but it's quite expensive. If you're not sending huge volumes it might not worth it. The only way to measure the IPR is actually to have a certain number of test inboxes... In other words: the only way to chech that your email is not in the spam folder is to make the test and see what happen. There is not other magic solution and that's what Return Path is doing.
This means that when you hear about people claiming they have a 99% deliverability / delivery, it might be true be it just means that the email was "accepted" or "delivered" by the ISP. It's a lot, but it's not everything!
What you should do is the following: use an ESP focusing on deliverability. Personally I work for Mailjet. I believe it's the best value you can get: personalized DKIM and SPF are provided for free, you get the antispam scorings, the analytics, Ip reputation monitoring, throttling, etc. It's an all in one tool to avoid the headaches of optimizing yourself. It's more expensive that Amazon SES because you get a lot of added value services, but it has much lower prices than a lot of traditional ESPs!
Bottom line is: optimizing everything yourself is a full time job. Knowing exactly if an email is in the inbox or not will cost you a lot. The best way to proceed is to:
respect the best practices (opt in, not too much images, no red, etc.)
get some metrics such as open rates, click rates, delivery, etc. and watch their evolution over time. Any change from one sending to the other might be a signal for a problem you want to investigate.
Use a tool that takes care all the deliverability optimizations
Mailjet is cool because no matter which plan you pick, you get to use all the options. But if you want a full overview of what is existing, check out this comparison table:
http://socialcompare.com/en/comparison/transactional-emailing-providers-mailjet-sendgrid-critsend
If you're a perfectionist who wants to finetune the layout, how the emails are displayed etc. Check out Litmus, it's also a quite powerful tool!
http://litmus.com/
Simple answer: Use Mailgun!!!!
http://mailgun.net/
They will do all of your email deliverability and setup for you and give you a powerful API to build on! They are amazing. You'll never have to worry about domain keys or SPAM filtering again!
You should also check that your IP is not on any of major blacklists. dnsbl.info
This will at least give you an idea if you actually are getting flagged as spam.
For the past two years, we've used the service DeliveryMonitor.com. However, they've stopped accepting new applications which is a big red flag...
I'm currently evaluating the service from emailreach.com using their free trial
... We are now using DeliveryWatch.com with pertty good results thus far...