Factors That Can Help You Determine Your Email Deliverability

Factors That Can Help You Determine Your Email Deliverability

Email deliverability issues can cost brand money by sending emails to spam folders or blocking them entirely. While deliverability may seem uncontrollable, inbox placement is governed by some factors that are all under their direct or indirect control.

Let’s take them one by one.

Volume of Email

The more email a company sends, the more it is scrutinized. Large senders will naturally struggle more than small senders to maintain good deliverability.

Spammers often try to send a large volume of email out of the blue, so sending patterns are important. Inbox providers like to see consistent sending volumes from a brand. That doesn’t mean brands have to send the same amount every day or week, but regularity is good. This means brands must gradually increase volume weeks before high email frequency seasons, such as the holiday season for retailers.

Small senders have an advantage here as well, as they tend to use shared IP addresses with other small senders. This helps mailbox providers see consistent email volume.


Choosing an ESP’s servers, setup, and controls affects how mailbox providers perceive emails, so choose wisely. The good news is that most ESPs automatically authenticate customers’ IP addresses and domains. Authenticating your email with SPF and DKIM standards, as well as setting up DMARC records, is important for deliverability, so double-check with your ESP.


Word choice, punctuation, and image/text ratio used to be important email filtering factors, but not anymore. Inbox providers now pay attention to email code.

First, they don’t want to see embed tags or JavaScript. Second, they want emails that are properly coded, with all tags closed.

Third, they closely examine URLs. Deliverability will suffer if a brand’s emails contain links to bad websites. They’ll also have issues if they use URL shorteners, which spammers frequently use to hide their links.

Spam Complaints

If more than 0.1 percent of a brand’s subscribers report spam, their emails may be blocked or junked. Because subscribers cannot easily unsubscribe or trust a brand’s unsubscribe process, they report senders’ emails as spam. Still, most reputable brands can easily stay below that threshold.


Mailbox providers now pay attention to positive feedback as well. They also heavily weight positive feedback like opens and other actions that show users want to receive emails from a sender.

Positive engagement is now one of the key factors affecting deliverability. As a result, senders must manage inactive subscribers, reducing email frequency to less active subscribers, and eventually suppressing inactive subscribers. Improve engagement and deliverability by sending more targeted, personalized, and automated campaigns.

Unfortunately, Apple’s Mail Privacy Protection will make it difficult for senders to track opens, which has been important since mailbox providers started tracking engagement. With Apple Mail users who enable Mail Privacy Protection, Apple makes it difficult to identify inactive subscribers.

Bounces and Spam Traps

Mailbox providers also want to see that brands are not sending to bad addresses, of which there are two types. First, they don’t want brands sending emails to invalid addresses. When senders do this, their emails “hard bounce” and their ESP automatically blacklists those addresses. A brand’s deliverability suffers if more than 2% of its emails hard bounce in a month.

Second, sending emails to spam traps demonstrates poor subscriber acquisition practices, as inbox providers and blocklist operators use these email addresses to identify spammers. For example, pristine spam traps are email addresses only email scraping software can find. Sending to these addresses shows a brand is either using or buying such software. A big red flag for mailbox providers.

Aesthetics of Spam Filtering

Mailbox providers fine-tune their filtering algorithms to account for changes in email behavior and spammer tactics. Many changes have occurred over time, but two have radically altered how marketers manage deliverability.

First, engagement-based filtering means brands can no longer thrive by not offending recipients. This stopped senders from bloating their lists with inactive subscribers who didn’t complain. Marketers today must always balance quality and quantity when it comes to email lists.

Second, the introduction of domain-based reputations made it impossible for brands to simply switch IP addresses to avoid bad sender reputations. Senders who have issues with deliverability must now change their habits to regain favor with mailbox providers.

Because of these two changes, marketers should keep an eye on all deliverability-related factors to avoid issues.

Leave a Reply