[iOS] Investigation into the specifications of "This message is from a mailing list."

Conclusion: It's best not to tap if you're unsure

To conclude,

If it's an unfamiliar or suspicious email, it's best not to tap it.

If it's a spam email, you might inadvertently tell the sender, "This email address is in use."

On the other hand, if it's a trustworthy email, tapping it is fine, but personally, I think it's better to change newsletter subscription settings via the "unsubscribe" link within the email or through a dedicated "My Page."

Therefore, if it's a suspicious email, block the sender.

What happens when you unsubscribe?

Let's actually tap "Unsubscribe."

A pop-up will appear, so tap "Unsubscribe."

Then, nothing happens, but...

Looking at the outbox, there's a trace of something sent.

Was it successfully unsubscribed...?

Since it depends entirely on the sender's system, there's no way to confirm it.

Is it spam?

Not necessarily.

In my case, this message appeared on a legitimate notification from a credit card company.

On the other hand, I believe this message can also appear on spam emails.

In that case, sending an unsubscribe request could inadvertently tell the sender, "This email address is in use."

If an email is even slightly suspicious, respond by blocking the sender instead of unsubscribing.

Under what conditions is it displayed?

This message is displayed under the following conditions:

Apparently.

Simply put,
if an unsubscribe address is explicitly stated in the email, it seems to send an email to that address saying "please don't send any more."

As mentioned earlier, whether sending it will definitely unsubscribe you is not certain, as it depends on the sender's system.

<?php
$to = "to@example.com";
$subject = "test";
$message = "test message";
$headers = "From: from@example.com";
$headers .= "\r\n";
$headers .= "List-Unsubscribe: <https://blog.knis.jp>,<mailto:from@example.com>";
mail($to, $subject, $message, $headers);

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