What happens after you hit send

It seems like email marketing has been around forever. While not as new and exciting as other marketing channels like social media and digital advertising. Email still holds strong as one of the most effective marketing channels. An average return of $42 for every one dollar spent (DMA, 2019). You might think its effectiveness lies in its simplicity. After all, you just need to hit send and you are done, right? Wrong. Email is actually quite a complex marketing channel. Reaching its true potential takes some work. Unless you have access to the right data. Plus, know where to look unexpected problems may arise. To help marketers understand and take advantage of this channel we created a guide to walk you through the basics of email marketing. In this guide we cover how email really works, as well as terminology, tips, and pitfalls to avoid.

What happens when you hit send

When a marketer hits send, an email’s journey has just begun. Before an email reaches its final destination, it must pass through many filters designed to determine the validity of the message and decide where it should be placed. Only when an email successfully navigates these filters can it arrive in the inbox. There is no avoiding spam filters. They are a necessary part of the email process. Instead, you need to understand how filters work, what they check for, and how to make sure your messages get a passing grade.

What is a Filter?

Filters are a program mailbox providers use to analyze incoming email according to specified criteria and determine where to place them. Originally, filters were designed primarily to distinguish spam from legitimate email, and either block spammy messages or place them in the spam folder. Today, some mailbox providers also use email filters to categorize messages for inbox organization purposes (e.g., social media and newsletters).

Why Do Mailbox Providers Filter Email?

Mailbox providers have strong motivations to use spam filters. While spam is annoying, it can also be dangerous. Malware and phishing are hugely profitable for scammers and can be costly for consumers—the mailbox providers’ customers—as well as the mailbox providers themselves, who face intense market competition. In addition to protecting their mailbox users, spam filters also drastically reduce the load on server resources. Considering that almost half of all mail sent globally is spam, that’s a lot of mail to analyze.

How Do Filters Evaluate Email?

Mailbox providers look at three main aspects of mail when making filtering decisions: 1. Source of the email 2. Reputation of the sender 3. Content of the email

What is the Source of an Email?

The source of an email is the identity of the sender. In evaluating an email’s source, spam filters look at factors such as past sending behavior, the age of the address the mail is being sent from (i.e., your IP address and domain) and whether the sender is authenticated (allowing the mailbox provider and the subscriber to confirm the identity of the subscriber).

Email sent from new IP addresses and domains is treated with caution by mailbox providers. Senders with longterm IP addresses and domains and those that use authentication techniques are seen as more trustworthy. Don’t change your IP address if you don’t have to If you are experiencing deliverability issues, changing to another IP address won’t solve the issue. In fact, you may be even worse off than before, as mailbox providers throttle messages from new IP addresses. Use a dedicated IP address On a shared IP address, you are not the only one contributing to your reputation. Despite your best efforts, if another sender on your shared IP address fails to follow good sending practices, your program will also be affected.

If using a new IP addresses, make sure you properly warm it up Gradually begin sending a small volume of mail, ideally to your more engaged users to build up a positive reputation on your new IP address.

Authenticate your email program Mailbox providers view authenticated email as more trustworthy and are more likely to deliver it to the intended recipient. The most important email authentication protocols are SPF, DKIM, and DMARC

What is Sender Reputation?

The reputation of an email sender is a score that indicates whether they’re viewed as a legitimate sender or a spammer. It is calculated using algorithms that leverage millions of data points to evaluate past sending behavior and judge the validity of the sender. Based on the strength of the reputation score, mailbox providers will make filtering decisions about the email coming from a sender. Some of the parameters leveraged to determine a reputation score are: 1. Complaints 2. Spam traps 3. List hygiene 4. Volume 5. Blacklists Until senders take steps to improve their reputation, their messages will continue to be delivered to the spam folder.

How to improve your sender reputation

Monitor your sender reputation Always check your reputation score before you send and messages to ensure poor reputation won’t impact your campaigns. Keep your list clean Spam traps, unknown users, and unengaged subscribers can have a detrimental impact on your reputation. To validate whether the addresses on your list belong to a real person, run your list through a list hygiene service. Sign up your feedback loops Avoid possible damage from subscriber complaints by signing up for feedback loops. Each mailbox provider offers its own feedback loop service to alert senders when a subscriber complains about a message. Depending on the composition of your list, you may not need to sign up for every feedback loop available so identify which ones are most valuable to your program before signing up.

What content are filters looking at?

Content analysis technology has the capability to scan every part of an email, including the header, footer, code, HTML markup, images, text color, timestamp, URLs, subject line, text-toimage ratio, language, attachments, and more. For some content filters, every single part of the incoming message is scrutinized. Other content filters may look at only the structure of an email, or they might simply parse URLs out of the message and reference them against blacklists.


Check your HTML Most emails today are created in HTML, so having a nicely formatted HTML message is a good start. Broken HTML can lead to a poorly rendered message and generate complaints if recipients believe it’s a phishing attempt. Make sure your HTML is free of syntax errors and formatting errors. Test your message before you send Testing message content in a pre-deployment tool such as Everest’s Inbox Preview can help to identify potential spam filter issues before you send. Once you identify content that is being flagged by spam filters, continue testing to isolate what is causing the issues (for example, subject line, URLs/links, text, and/or images).