Unfortunately, the answer is:
- all of the above
Email bounce messages are both annoying and informative. They can help you fix a problem with an email you’ve sent, or they can simply be another message in a big pile of spam.
Unfortunately, about the only thing you can count on is that you cannot count on bounce messages.
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What’s a bounce?
Just to be clear, “bounce” is the term we use when email we send causes an error message (also in the form of an email message) to be returned. Usually, though not always, the error message includes the original email.
The email you sent has not been delivered, and is thought of as having “bounced back” to you.
Hopefully, the error message contained in the bounce gives you information as to why it bounced.
What is this “closed” you speak of?
First, I have to ask, what does you mean by a “closed” account in your question? It could mean many things, including:
- The user stopped using it. Email will still be successfully received, and simply accumulate. There’s nothing here that would cause a bounce.
- The user could have “closed” the account, but the ISP hasn’t released or actually deleted it yet. Email may still accumulate, without bouncing, until cleanup happens after some period of time.
- The account exists, but is actually, honestly, closed.
- The account no longer exists (or never did).
While some of those things you might think of as being “closed”, not all of them will cause a bounce, and in fact none of them are required to cause a bounce.
With the ever-increasing influx of spam, many ISPs choose to ignore mail destined for invalid or closed destinations. Why? To avoid flooding the internet with even more noise.
You’ve probably received bounce messages for email you didn’t send. Spammers have “spoofed” the email such that it looks like it’s coming from you, and then blasted it out to anything they can find that looks like an email address. Some ISPs generate bounces if those addresses are invalid, and that’s what you’re seeing. Other ISPs don’t generate bounces, since they’re as bogus as the spam that caused them.
So, the bottom line here is that an ISP may, or may not, return a bounce on an invalid email address – or on any error, for that matter.
But it gets worse.
Because so many bounce messages are the result of spam, even if a returning bounce message is the result of some email you actually did send, some spam filters are now filtering those bounces out as spam.
So even if the recipient’s email provider does send a bounce, there’s actually no guarantee you’ll get it!
Bounces usually happen, but…
Now, lest you give up all hope, I will say this: most of the time, bounces are generated and received and work pretty much as you expect. But the problem is that you can’t count on it.
If you send an email to someone and don’t get a bounce, that tells you nothing. They could have received the email, or not.
You can tell if they got it only if they reply or somehow act on the information you included in the mail.
But if you hear and see nothing, you just can’t tell whether or not the email arrived. (And of course, you certainly can’t tell if they actually read it if it did. 🙂 )