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How to Keep Your Marketing Messages Out of Spam Folders

Understand Email Deliverability

Katelyn StaabenKatelyn Staaben/Digital Marketing Strategist
June 25, 20184 min read

Do you really know what happens to marketing emails after you’ve sent them? Sure, you can track click-through rates, open rates and bounces, but how can you tell if your emails land in correct inboxes or land in spam folders?

Every email marketer should think about email deliverability. According to a study by Return Path, 21% of opted-in emails fail to arrive in the intended inbox. This happens because the email runs into a closed inbox, which results in a bounce, or because the email redirects to a spam or trash folder.

Some deliverability factors are beyond marketers’ control. But many are within grasp. Where your email lands depends on three key factors: identification protocols, the content of your message, and your sending reputation.


Identification Protocols

The first thing an inbox examines is whether your email comes from a source it can identify, based on these protocols:

  • Sender Policy Framework (SPF)
  • DomainKeys Identified Mail (DKIM)
  • Domain-Based Message Authentication, Reporting, and Conformance (DMARC)

These three things tell the inbox who you are. Generally, third-party email marketing firms require you to set up these protocols when you set up service. A free tool, Mail-Tester, can help you find out whether or not you have optimized the protocols for your email campaigns.




Mail-Tester can also help with content considerations.


Sending Reputation

Your sending reputation rests on several factors, including:

  • How often your emails are marked as spam
  • How often your emails bounce, especially if they are hard bounces
  • If your sending IP or domain is blacklisted

Reputation is measured at both the IP and the domain levels.


IP Reputation

IP reputation counts most in email deliverability. It is based on the history of emails sent by the source IP address of the current email. The source IP could be dedicated, for a larger sender, or shared. Dedicated IP addresses provide more control over IP reputation, but they pose certain challenges and are often not viable for small to mid-sized organizations.


Shared IP Addresses

Most businesses distribute email marketing through a shared IP. Email service providers (ESPs) use many different IP addresses to send out emails for their clients. Typically, with an ESP, your IP will switch among several addresses, based on availability. The likelihood that your email will be delivered ties not only to the emails that you send, but also to emails of other clients who use that ESP.

Reputable ESPs counter this contamination by monitoring spam and bounces. They know that one bad sender can spoil the email deliverability of their entire client base, so they make every effort to keep bad apples out of the barrel.

Vet your ESP to determine how the service monitors potential spam issues relating to shared IP addresses.


Dedicated IP Addresses

Only a dedicated IP address for your emails can fully control your IP reputation. Many email service providers (ESPs) offer a dedicated IP option, at higher cost than shared services, for frequent, large-volume senders. These costs, along with minimum volume requirements, put dedicated IP addresses beyond the reach of most small to mid-sized companies.

Even if a dedicated IP address is a viable option, you still need to “warm it up” to avoid being marked as spam. When an IP address abruptly goes from sending zero emails to hundreds, inboxes become wary and mark the sudden barrage as spam. Once marked as spam, a dedicated address, unlike a shared IP address, is very difficult to escape. That flagged IP will follow you even if you switch ESPs. You must start from scratch or slowly improve your reputation over time.


Domain Reputation

While IP reputation is still the main factor in email deliverability, domain reputation is growing in prominence as a way to more thoroughly judge the reputation of email senders.

Your domain reputation, based as it is on your website domain (for example,, will follow you even if you change ESPs. Most inboxes today consider both domain and IP when deciding where to send emails, so maintain good reputations on both fronts.


Message Content

Most regular email users identify spam at a glance. Certain common phrases, imagery or layouts immediately tip them off.

Your inbox behaves the same way. It tags certain phrases and email layouts that spammers use. If you use them, too, the inbox will likely push your legit email into spam. These triggers include:

  • Buzzwords, such as “Free” or “Promo”
  • More imagery than text
  • Very large emails (over 30 kb)
  • FW: or Re: in a subject line sent to a list
  • Excessive punctuation (!!!) or TOO MUCH CAPITALIZATION
  • Lack of alt text on images
Katelyn StaabenKatelyn Staaben/Digital Marketing Strategist

Katelyn Staaben is a social media strategist and digital marketer with a background in developing strategy for B2B organizations. Certified in conversion writing through Conversion XL and Google Analytics, she supports the Northwoods digital marketing and account teams by contributing ideas to web design projects, social media, SEO, digital strategy consulting, and content management implementation.

Connect with Katelyn on LinkedIn | Read Katelyn Staaben's Blogs

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