Zombie email: Part 2

In zombie email: part 1 I talked about how email addresses were tightly tied to internet access in the very early years of the internet. We didn’t have to worry about zombie email addresses because when an account was shut down, or ignored for a long time then mail would start bouncing and a sender could stop sending to that account.
There were two major changes to email accounts in the early 2000’s that led to the rise of zombie emails.
People started decoupling their internet access from their email addresses. Free addresses were easy to get and could be checked from everywhere. No longer did they have to dial in to get email, they could access it from outside the office and outside the home. Mobile devices, including the first generation of smart phones and laptops, helped drive people to use email addresses that they could access from any network. The easy access to free mail accounts and the permanence led people to adopt those addresses as their primary address.
When people changed addresses, for whatever reason, they didn’t have to stop paying. There was no way to tell the free ISPs to stop accepting mail for that address. Free mail providers would let addresses linger for months or years after the user had stopped logging in. Sometimes those addresses would fill up and start bouncing email, but they were not often turned off by the ISPs.
The lack of purging of abandoned addresses was the start of dead addresses accumulating on mailing lists. But there weren’t that many addresses in this state, and eventually they would fill up with mail. When they were full the ISP would stop accepting new mail for that account, and the address would bounce off a mailing list.
Everything changed with the entrance of Gmail onto the scene. When Gmail launched in 2004 they were providing a whole GB of storage for email accounts a totally unheard of storage capacity. Within a year they were providing multiple gigabytes of storage. Other freemail systems followed Gmail’s lead and now all free accounts have nearly unlimited storage. Plus, any mail in the spam folder was purged after a few weeks and bulk mail doesn’t count against the users’ storage quota. Now, an abandoned email account will almost never fill up thus senders can’t use over quota bounces to identify abandoned accounts.
Now we’re stuck in a situation where SMTP replies can’t be used to identify that there is no one home inside a particular email account. Senders can’t distinguish between a quiet subscriber and an abandoned address. ISPs, however, can and are using zombie addresses as a measure of a senders reputation.
On Monday we’ll talk about why and how zombie addresses can affect delivery. (Zombie emails: part 3)
Tuesday, we’ll talk about strategies to protect your list from being taken over by zombies. (Zombie Apocalypse)


  1. Zombie email: Part 1 – Word to the Wise says

    […] Zombie Email: Part 2 […]

  2. Steve White says

    I guess it’s too much to ask for the ISPs to let us know about the zombie accounts so we can update our lists accordingly?

  3. Huey says

    In a word: yes. If you’re going to send mail that nobody reads, that’s valuable to them in that they can use that as part of their metrics for determining how much mail you send is actually wanted, and they have no motivation to do additional work to devalue that resource, just because you’ve asked them to.
    The solution isn’t for the ISPs to do extra work just to help you, the solution is for you to send less mail nobody reads, and THAT will help you.

  4. Steve White says

    If the ISP doesn’t tell me specifically about zombie accounts, how do I know about them? I understand that they may use it as a metric for deliverability. My typical client (that sends marketing messages) has lists that are a mixture of old and fresh addresses. (Of course, the clients can segement any way they want) Everything’s going well but like plaque that builds up in our arteries, so too the list will one day be full of too many “zombies.”
    I’ve noticed a lot of yahoo email addresses are used by customers who dont want to give their real email address (forum confirmation emails of all things).
    Anyway, this is nothing new. Hotmail has been turning bounced addresses into traps forever now. At least in their case they actually do give bounce notifications before it turns into a trap. Hey, now that makes sense.

  5. laura says

    Hotmail has been turning bounced addresses into traps forever now. At least in their case they actually do give bounce notifications before it turns into a trap. Hey, now that makes sense.
    Not really. I have a hotmail account I registered back in 1996. For a while if I didn’t log into it every 6 months or so (It was an account I used to post to Usenet, not for “real” mail) then it would be disabled and I’d have to recover it. That changed and now there is no recovery.
    I’m working on another article about spamtraps that’s not quite ready yet. But I can say that the statement but “hotmail turns all abandoned accounts into spamtraps” is totally untrue.

  6. Steve White says

    Regarding Hotmail turning bounced email addresses into traps – from their deliverability guide –
    “3. Spam trap addresses – These are addresses (in some cases a domain) that have never been signed up to receive any kind of message or have been deactivated after prolonged inactivity by the ISP.”

  7. laura says

    Steve: That’s a definition of spamtrap, yes. I’m not sure how a definition you, I and Hotmail agree on is relevant to what we were disagreeing about. The definition of spamtrap does not mean that Hotmail turns every abandoned account into a trap. I know for a fact that they don’t because my Hotmail address has been “abandoned” more than once.

  8. Steve White says

    Hotmail’s been doing it since 2006:
    If your abandoned account was turned into a trap – how would you know? The SNDS/JMRP systems do not reveal traps. It’s entirely possible that while your account was in abandoned status it was a trap.

  9. Al says

    Q: If the ISP doesn’t tell me specifically about zombie accounts, how do I know about them?
    A: Zombies don’t respond to emails. They don’t reply, click, open, or otherwise interact. See: “Engagement,” and pay attention to engagement. It’s a deliverability best practice that just about anybody spouting best practice guidance has been spouting for a year or more.

  10. Zombie emails: part 3 – Word to the Wise says

    […] week, in Zombie emails: part 1 and part 2 I talked a little about the history of email addresses and how changes in the ISP industry in the […]

  11. The Proverbial Barry says

    marketers dont have to be scared of zombies
    zombies only eat branes

  12. The Received Blog says

    […] the comments for part 2 of Laura’s series, there’s a bit of a debate about abandoned addresses being turned […]

  13. Don’t take my subscribers away! – Word to the Wise says

    […] abandoned the email address and never check it. I wrote a series of posts on Zombie Emails (Part 1, 2, 3) last September, finishing with suggestions on how to fight zombie email addresses. Still, I see […]


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