Deliverability 101: Back To The Basics Q & A

During our recent webinar titled Deliverability 101: Back to the Basics, we had a great turnout and lots of well thought-out questions that we, unfortunately, didn’t have to time to answer. After the session ended, we compiled those questions and we’ll be addressing some of the best and most-asked ones here.

Q: You mentioned that high hard bounce rates can cause delivery issues. What bounce rate should we stay below to avoid problems?

A: Each ISP or mailbox provider will weigh metrics like bounce rate differently, and each will have different thresholds. In many cases, these thresholds are dynamic and may increase or decrease based on other factors including sender reputation, volume sent, and engagement.

Likewise, many email service providers vary their recommended hard bounce rates. The absolute best practice would dictate keeping average hard bounce rates below 1% of your mailing volume. Hard bounce rates below 3% are still considered acceptable by most providers, while rates above 5% are typically considered cause for concern. Hard bounce rates of 5-10% or above may even cause an ESP to take action on your account, including suspension of sending privileges.

Q: How can we best identify spam trap addresses in our lists?

A: The short answer is “you can’t.” Spam traps are designed to be known only to the person or organization maintaining the trap. Hitting spam traps regularly is a signal that your list acquisition or hygiene practices need improvement. In most cases, if your list is obtained by clear permission – not obtained through purchase, harvesting, or a third party – spam trap hits will be minimal.

Q: Is there a legal way to reengage users who unsubscribed in the past?

A: In the US, once a user has requested to be unsubscribed from your mailings, you have up to 10 days to process that request. Any additional email sent to that user, other than purely transactional content, is considered a violation of CAN-SPAM. Canada’s CASL also requires honoring unsubscribe requests and carries even more hefty fines for violations. If you feel you absolutely must reengage with an unsubscribed user, you’ll want to do it by some means other than email.

Q: Are hard bounces caused only by invalid addresses, or are there other possible causes?

A: As we discussed in the webinar, a hard bounce is any permanent error returned by the receiving mail server (prefaced with a 5xx bounce code). What exactly is classified as a hard/permanent bounce depends somewhat on the mail server. Many servers are set up to reject mail from blocked IP addresses or domains while returning a 5xx error code. As such, those are technically classified as hard bounces, even though the block may be temporary.

In those cases, WhatCounts (along with most other ESPs) has specific bounce processing tools that will try to identify which hard bounces were caused by blocks as opposed to invalid addresses. Usually this is accomplished by reading the text that accompanies the bounce code. Those bounces that are determined to be caused by mail blocks are not included in the “Hard Bounce” category within WhatCounts reporting, and those addresses are not automatically suppressed like other hard bounces.

Q: Can my IP address be blacklisted as part of a larger block because of mail sent by someone else on a different IP address?

A: Yes, but it’s not likely. Usually this will happen in one of two situations:

1. The blacklist operator sees a pattern of spam coming from IPs throughout the range of IP addresses. If the spam often comes from more than one IP at a time, or moves across different IPs within the range, the operator will assume the entire range is problematic.

2. One or more IP addresses in a range are blacklisted and the sender continues to send spam, ignoring the blacklist. In this case, the blacklist operator will often list the entire IP range in an attempt to “get the attention” of the sender. They know that often these senders are sharing a range with others and by impeding their mail, the offender will be motivated to stop (possibly by their bandwidth provider).

If you are a client of an ESP, both of these situations are quite rare. ESPs like WhatCounts monitor IP ranges regularly and take action to resolve any blacklistings quickly, as well as ensuring spam is not being sent over their networks.

These are just a few of the questions we received during our webinar, but please feel free to comment or reach out with your additional questions.

As always, feel free to contact WhatCounts Support if you have questions specific to your WhatCounts experience.