These days, so much important communication is conducted by email that we expect it to be rock solid. So when emails don’t arrive—or even worse, we don’t know that they didn’t arrive—it can be worrisome.

Last November, our friends at Infoworld reported that Apple’s iCloud email system silently blocks emails containing certain phrases. And that hasn’t changed in the intervening months, as Macworld UK reports.

Granted, the phrases in question may not be the kind that you’re likely to exchange with your correspondents.

Through our own rigorous testing, we’ve managed to confirm that emails containing the phrase “barely legal teen” are simply never delivered to iCloud inboxes. In fact, we found that even emails with the offending phrase contained in an attached PDF—even a zipped PDF—were blocked.

Even if you, like us, would almost never receive a legitimate email with such a phrase, this could still be problematic. For example, had you emailed someone about the fact that Apple blocks emails with the phrase “barely legal teens,” that email would itself never arrive. And if, as with the person who originally reported the issue to Infoworld, you were attaching a work of fiction with such a phrase, that too would be blocked.

In our tests, we did find that the filtering only occurs on inbound emails, not outbound emails. So you can at least send emails from your iCloud account with the phrase “barely legal teens” to your heart’s content, though don’t be surprised if you start to get funny looks from all your correspondents.

This email will never arrive.

Having discovered that, we also located a workaround that allows emails with the phrase “barely legal teens” to arrive in your iCloud inbox: If you send an email containing the filtered phrase, and the recipient replies to it, the reply will show up in your inbox. However, that’s hardly a solution to the overall problem, unless you plan to ask all of your email correspondents to never send you brand new messages, but instead always reply to one of your messages.

We contacted Apple for their comment on the issue, and a spokesperson told Macworld “Occasionally, automated spam filters may incorrectly block legitimate email. If the customer feels that a legitimate message is blocked, we encourage customers to report it to AppleCare.”

Why that’s a terrible answer

Of course, that introduces a sort of existential dilemma here: How do you report the non-arrival of an email that you never received?

If it’s an email whose arrival you’ve expected then, yes, you might very well be nonplussed when it didn’t arrive. But we all get plenty of emails that we don’t expect—and some of them aren’t even spam. Reporting that you’re missing an email that you don’t even know someone sent you is a positively Sartrean task.

To be clear, the problem is not that Apple is flagging terms that are most often used in unwanted, spam messages—it’s the lack of transparency about this filtering. Apple is flagging messages that it seems very sure are spam, but it has no real system in place for dealing with false positives—messages that are filtered, but aren’t actually spam.

Even though Apple offers a Junk folder, these filtered messages never appear there.

What makes this more confusing for some users is that Apple already has spam handling procedures in place: Both iCloud and Mail on the Mac offer Junk mail folders, but the “barely legal” messages never even appear there. Apple presumably feels so certain that specific messages are spam that it’s choosing to bypass the Junk folder entirely. That could be okay, if Apple did more to let users know what was happening.

Other services have different ways of handling problems like this: Many send you reports of messages that were blocked, and allow you to indicate when an email has been mistakenly flagged.

Apple’s filter is also completely opaque to users: While we now know that the phrase “barely legal teens” is blocked, we don’t know what other phrases might be on Apple’s blacklist. And there’s no way to find out, short of trying to repeatedly send emails with potentially triggering phrases in them.

And even if you do discover something Apple is filtering, calling up AppleCare and telling them that you didn’t receive an email containing “barely legal teens”—or some other potentially crass phrase that you might discover Apple filters for—is not an experience anybody really wants to have.

Moreover, our sources indicate that even if you do contact them, AppleCare staffers can’t actually recover the missing emails. So you can report that you’re missing an important email, and maybe the AppleCare reps can do something—whitelist the sender, perhaps?—but you won’t actually get the missing message unless you tell the sender to try emailing it again.

At best, you might hope that multiple reports of this kind might spur Apple to change its policy, but it seems unlikely that Apple will decide to stop filtering for those phrases, no matter how many people complain about not receiving emails with potentially offensive phrases.

Junk in the trunk

Some might be willing to forgive this practice if Apple’s approach had magically solved the spam problem. But spam still occasionally gets through iCloud’s many filters—and that’s why the service offers a Junk folder. Apple’s choice to delete certain messages before they arrive may help in the war against spam, but there’s too much risk of collateral damage.

It’s also worth noting that there may well be some customers who genuinely wish to receive emails containing precisely the sorts of content Apple’s filters seek to ban. While Apple’s prudish tendency feels at least defensible on the App Store, it seems puritanical when it comes to pre-screening a customer’s private inbox.

But as distressing as all of this might be for users, Apple is technically within its rights when it filters your email. As Infoworld points out, Apple’s iCloud Terms and Conditions include this policy:

You acknowledge that Apple is not responsible or liable in any way for any Content provided by others and has no duty to pre-screen such Content. However, Apple reserves the right at all times to determine whether Content is appropriate and in compliance with this Agreement, and may pre-screen, move, refuse, modify and/or remove Content at any time, without prior notice and in its sole discretion, if such Content is found to be in violation of this Agreement or is otherwise objectionable. (Emphasis added)

Time for a change

So, where does that leave iCloud email users? Some may feel that they aren’t too bothered by this practice—we could even imagine that there are those who might consider Apple’s aggressive spam-blocking a selling point.

But those who count on all their emails arriving reliably may want to reconsider their choice of email providers. We don’t know what phrases Apple blocks, and we don’t know when messages have been flagged for such blocking. That’s an unacceptable situation for many users.

And it’s not as if there’s a lack of good, free email providers with years of spam-blocking experience: Google, Yahoo, and Microsoft all spring immediately to mind. And—as far as we know, anyway—those services aren’t “helpfully” blocking any emails without telling their users.