(Part Three of a Three Part Series on How to Improve Email Deliverability)

by Wendy Roth

 

When No News is Bad News

Your email could be blocked—and you don’t even know it. Even the best successful delivery statistics can hide deliverability problems.

There are of course many legitimate reasons why email messages can’t be sent. People switch jobs or change ISPs, and don’t bother to update their email address with everyone. But to really know why individual recipients aren’t getting your mail, you’ll need to look at the rejection messages—the bounces.

Bounce Basics

A failed delivery is commonly called a bounce, because the undeliverable message “bounces” back to the sender.

A “soft” bounce is typically due to a transient problem—the recipient’s mailbox is full, for example, or the recipient mail server is too busy.

Just because a bounce is soft doesn’t mean that repeated attempts to send to the address will be successful. No matter how many times a sender tries, a message will never be deliverable to bob@aol.cmo. Even if the address is legitimate, the recipient may have abandoned the email account so that the mailbox is perpetually full.

A “hard” bounce is generally the result of a permanent problem, such as the recipient address doesn’t exist. In that case, you’ll see an error like this one:

550 Requested action not taken: mailbox unavailable 
550 JOHNB@EXAMPLE.COM is not a valid user 

Hard bounces tell your mail server to stop trying to send to this address.

When a Bounce is a Block

Spam is a scourge not just because it wastes your time to delete it from your inbox, but because it uses your ISP’s network resources. A mail server that is busy processing spam has less capacity to handle email people want to receive. It may seem like spam is free, but there is in fact a cost—unfortunately, that cost is largely borne by the recipient.

The usual tactics ISPs and organizations have taken to combat spam is to block suspect messages or senders as soon as possible so as to keep their resources free for legitimate mail. In accordance with the “rules” of the internet, they are supposed to inform the sender the reason why the mail was refused.

So, a “soft” bounce may be the result of the receiving mail server refusing the connection, either because it’s in general too busy or because the connecting mail server is considered to be spamming. These refusals look something like this:

Server example.com is not accepting connections 
Connection refused by: example.com 

Sometimes, if your server is being “temporarily” blocked, the message will be categorized as a “soft” bounce, too:

421 anti-spam.example.com has refused your connection 
as your mail server has been temporarily blacklisted 

Many ISPs use “hard” bounces to reject messages they consider to be spam. Here’s an example of that kind of message:

550 Blocked for abuse. Please contact the administrator
    of your ISP or sending mail service
554 Transaction Failed Listed in deny list 

While delivery failures are unfortunate, they help you save time and resources because they let you prune the dead wood from your list and keep it full of active, interested recipients.

Messages that say your mail is being blocked as spam, while aggravating, are also helpful. If someone at a blacklist or at an ISP sees your mail as a problem, it’s good to know about it so you can contact them and resolve it.

There’s a bigger problem than knowing you’re being blocked—it’s not knowing. More and more frequently, the same transaction messages that should be legitimately used to tell you that a recipient no longer exists are being used to reduce spam.

If a domain with previously high deliverability rates suddenly shows a large number of non-existent users, it may be that there’s been a lot of turnover—or it could be that you’re seen as a spammer and they’re trying to make you go away.

The idea is that spammers may not stop trying to send mail to an address if they’re being blocked—they’ll just go to another ISP or change their content so they can slip through. But if they receive a message that a recipient no longer exists, they’ll be tricked into taking that address off the list regardless of where they go.

It’s hard to know how effective this tactic is against spammers; do they really remove inactive addresses? But it can be very “effective” against consciencious senders, who unwittingly remove these addresses.

If there is a sudden increase in dead addresses at a particular domain, it could be that there have been massive layoffs—or that your mail isn’t welcome anymore. See if the same people are undeliverable several times in a row, or if they are still undeliverable if you change the format of your mail—plain text instead of HTML, for example.

The “Quiet” Bounce

Success at reaching all the addresses on your list is the ultimate goal. But reaching that goal doesn’t mean your worries are over.

A hundred percent success delivering to a domain without any delivery failures may mean every address at that domain is still alive and kicking, or it could mean that the ISP has given up. Instead of giving useful (or even deceptive) non-delivery notices, it could be just accepting all of your mail, and then dumping it in a bulk folder--or simply deleting it, without forwarding it to the recipients at all.

If a domain has more than a hundred addresses, you should see some failed deliveries from time to time. If you don’t, check and see if there are any actions from recipients at the domain in question. Are there any opens or clickthroughs at all? If not, it’s probable the mail isn’t getting through.

Take Action!

Once you know that your mail is being blocked, you can take action to ensure that it gets delivered.

• Change the format. If you’re sending in HTML, try sending plain-text.
• Slow your sending speed. It’s possible that you’re sending too quickly for the recipient mail server to respond.
• Email the technical contacts for that domain. Show that you are responsible and ethical, and they are likely to let your mail through. They may have suggestions on how to improve your email practices as well.
• Enlist the help of your recipients. If the technical contacts for a domain are unresponsive to you, they’ll probably listen to complaints coming from their customers.

There’s one action you absolutely SHOULDN’T take: change your sending IP address or domain in an attempt to trick ISPs that you are a different sender.

It’s tempting if your IP address is being blocked to simply change to another one that isn’t being blocked. But that’s exactly what spammers do. No matter where you go, your reputation will follow you. If your reputation is good, ISPs will be happy to work with you to ensure your mail gets delivered.