Catchall domains

Catchall domains accept any mail to any email address at that domain. They were quite common, particularly at smaller domains, a long time ago. For various reasons, most of them having to do with spammers, they’re less common now.

Most folks think catchall domains are only used for spamtraps. As a consequence, many of the address verification tools will filter out, or recommend filtering out, any address that goes to a catchall domain. They test this by trying to send emails to random addresses like sldqwhhxbe+ym7ajymw23gm0@clientspecific.domain.example.
But not all catchall domains are used for spamtraps. Every client here at WttW gets a domain assigned to them and those domains are catchalls. Emails to those domains go into a database for analysis. Clients (and I!) can create any LHS on the fly to test signups, look at mail flows. Having a catchall means we don’t have to actually configure any address so I can test multiple signups and encode the data about the signup in the to: address.
This works most of the time, at least until verification services mark those addresses as bad and they don’t get imported into the client’s processes. We have some workarounds, and can still get mail despite the services making assumptions.
 
 

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Email verification services

Just yesterday a group of delivery folks were discussing email verification services over IRC. We were talking about the pros and cons, when we’d suggest using them, when we wouldn’t, which ones we’ve worked with and what our experiences have been. I’ve been contemplating writing up some of my thoughts about verification services but it’s a post I wanted to spend some time on to really address the good parts and the bad parts of verification services.
Today, Spamhaus beat me to the punch and posted a long article on how they view email verification services. (I know that some Spamhaus folks are part of that IRC channel, but I don’t think anyone was around for the discussion we had yesterday.)
It’s well worth a read for anyone who wants some insight into how email verification is viewed by Spamhaus. Their viewpoints are pretty consistent with what I’ve heard from various ISP representatives as well.
In terms of my own thoughts on verification services, I think it’s important to remember that the bulk of the verification services only verify that an address is deliverable. The services do not verify that the address belongs to the person who input it into a form. The services do not verify that an address matches a purchased profile. The services do not verify that the recipient wants email from the senders.
Some of the services claim they remove spamtraps, but their knowledge of spamtraps is limited. Yes, stick around this industry long enough and you’ll identify different spamtraps, and even spamtrap domains. I could probably rattle off a few dozen traps if pressed, but that’s not going to be enough to protect any sender from significant problems.
Some services can be used for real time verification, and that is a place where I think verification can be useful. But I also know there are a number of creative ways to do verification that also check things like permission and data validity.
From an ESP perspective, verification services remove bounces. This means that ESPs have less data to apply to compliance decisions. Bounce rate, particularly for new lists, tells the ESP a lot about the health of the mailing list. Without that, they are mostly relying on complaint data to determine if a customer is following the AUP.
Spamhaus talks about what practices verification services should adopt in order to be above board. They mention actions like clearly identifying their IPs and domains, not switching IPs to avoid blocks and not using dozens or hundreds of IPs. I fully support these recommendations.
Email verification services do provide some benefit to some senders. I can’t help feeling, though, that their main benefit is simply lowering bounce rates and not actually improving the quality of their customers’ signup processes.

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Verifying addresses after POS collection

Collecting email addresses at point of sale is a challenge. Some stores collect the addresses electronically, where the clerk or the customer types addresses directly into the register. Smaller stores, however, typically collect addresses on a sheet of paper at the cash register. Eventually someone takes the list and types it into whatever contact management system the store maintains.
There are all sorts of errors that can happen when someone types in an address, but those errors are only compounded when the addresses are written on a sheet of paper for later transcription. Not all of us have perfect, copperplate handwriting and many of us have barely legible scribbles. In one case I had a sender read the tag in my email address wrong causing all their mail to me to bounce.
One person found an interesting solution to the problem of illegible addresses: using Facebook’s lookup to clarify illegible addresses.

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It's not about the spamtraps

I’ve talked about spamtraps in the past but they keep coming up in so many different discussions I have with people about delivery that I feel the need to write another blog post about them.
Spamtraps are …
… addresses that did not or could not sign up to receive mail from a sender.
… often mistakenly entered into signup forms (typos or people who don’t know their email addresses).
… often found on older lists.
… sometimes scraped off websites and sold by list brokers.
… sometimes caused by terrible bounce management.
… only a symptom …

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