The trouble with text-only email

Please consider subscribing to LWN Subscriptions are the lifeblood of LWN.net. If you appreciate this content and would like to see more of it, your subscription will help to ensure that LWN continues to thrive. Please visit this page to join up and keep LWN on the net.

Mozilla's manifesto commits the organization to a number of principles, including support for individual privacy and an individual's right to control how they experience the Internet. As a result, when Mozilla recently stated its intent to remove the "text only" option from its mailing lists — for the purpose of tracking whether recipients are reading its emails — the reaction was, to put it lightly, not entirely positive. The text-only option has been saved, but the motivation behind this change is indicative of the challenges facing independent senders of email.

The announcement that the text-only option would be removed was made (on the mozilla-governance list) by Michele Warther in late September. It quickly became clear that the community viewed this idea with a bit of skepticism, leading Warther to explain the reasoning behind the change:

Unfortunately text emails don’t have the same feedback loops available as HTML. A lot of people, of course, consider this to be a feature. But an unintended result is the negative effect that zero-interaction signals have on our reputation scoring: we have seen an increase in greylisting/blacklisting as a direct result of our text only emails, and that typically means we can’t send any email to *anyone* until it gets resolved.

The spam-ridden nature of the Internet forces anybody receiving email to be somewhat selective about what is allowed through. Only the most obscure and privately held email accounts can be exposed to an unfiltered mail stream without driving the owner insane. Much of the filtering applied is content-based, but much of it, especially at certain large web-based email providers, also takes into account the "reputation" of the sending site.

Some aspects of email reputation are straightforward. An IP address that is observed to be the source of volumes of spam will quickly find its way onto various online blacklists. When an IPv6 address is involved, the resulting block can cover a significant part of the address space, causing considerable collateral damage; this is why LWN's server is configured to send email via IPv4 whenever possible. IP addresses known to be used for residential Internet access are often penalized — if they are allowed to originate mail at all. Anybody who maintains their own email system can attest that reputation scoring also seems to have a significant random factor.

One metric that some sites evidently use is email sent to accounts that are known to be inactive, which is seen as a sign of a spammy originator. This, seemingly, is where Mozilla has run into trouble. One way to avoid this problem is to track which recipients are actually reading their email; any recipient who doesn't look at any messages for a period of time can then be unsubscribed. Then, in theory, email providers can see that the emails from a given source are actually of interest and refrain from putting up obstacles in their path.

The problem, of course, is that this tracking requires the "feedback loops" mentioned in Warther's message. These loops tend to take the form of tracking images that are fetched from a server belonging to the sender. The privacy implications of this kind of tracking are obvious: not everybody wants email senders to know when their mail was read and where the reader was at the time. Requiring this sort of disclosure would seem to run afoul of Mozilla Manifesto #4: "Individuals’ security and privacy on the Internet are fundamental and must not be treated as optional." But the alternative, Warther said, is an ongoing series of delivery problems for Mozilla's email in general.

There are other problems with tracking images and related mechanisms, starting with the fact that people who are paying attention tend to disable the loading of such images. Your editor recently received a complaint from a financial company that its emails were not being read; those emails were indeed read, they just weren't allowed to phone home and report that fact. Chances are good that this kind of blocking will increase in the future; not everybody wants to be a part of an unrequested "feedback loop".

In this particular case, it would seem that an acceptable compromise has been found, and the text-only option will remain. But, once a year, those subscribers will get a message asking them to click on a link to confirm their continued interest in remaining on the list. That should allow Mozilla to prune its inactive readers — a useful activity even without the reputation issues — without the need for involuntary tracking.

The fact that even principled organizations like Mozilla feel the need to employ tracking says something discouraging about the state of email, though, not that there was really any need for more evidence that the email system is broken. As the reputational checks become harder to pass, more users will be forced to use one of a small number of huge webmail providers (which have no trouble with "feedback loops") just to get their work done. Every kernel merge window features one or more developers having trouble getting their pull requests through to Linus Torvalds's Gmail account, for example. It's not clear what the solution to the email problem is, but the need is obvious.

