Best Practices to Ensure Successful Email Deliverability

Perhaps the most crucial part of a successful email campaign is to ensure that the email lands in the recipients’ inbox. Every creative effort, every analytical insight, every technological innovation that a marketer deploys is aimed towards ensuring that the email reaches the inbox of the intended recipient, and not get marked as Spam, or get lost in one of the many category folders that modern email applications come packaged with.

On the other hand, given the high volume of emails generated every day, email service providers and email client applications are constantly looking for ways to provide the best service to their users by reducing the clutter in their inbox.

Under these circumstances, it is very important for marketers to take all the necessary steps to protect their reputation, and avoid getting marked as Spam, or getting blacklisted by the email service provider.

This post aims to give marketers a set of recommended best practices followed in the industry to improve the email deliverability rate for marketers.

  • While Sending Emails

    • IP Warming: This is the process of slowly increasing the volume of emails going out from a new IP address. If there is a high volume of emails being sent from a new IP address, email service providers can view the IP as a suspicious one and blacklist it. For a new IP address, different platforms recommend different warm-up plan. Please note that the actual plan that MoEngage recommends from you may vary from this depending on various factors like your target outgoing email volume, your preferred connectors and domain preferences. For a customized IP warmup plan, it is highly recommended that you contact our team.
    • Using dedicated IP addresses: Email Service Providers sometimes use a shared pool of IP addresses to route emails belonging to multiple domains. However, if due to some reason an email client marks such a shared IP as fraudulent, all outgoing emails from that IP address pool will get marked as spam. This results in emails sent by a non-spamming domain also get marked as spam because it shares an IP with a spamming account. On the other hand, if a dedicated IP is not warmed correctly and used regularly, it might still get flagged as Spam because of sudden spikes in traffic through the dedicated IP address. Also, dedicated IP addresses are charged additionally by service providers. Hence, you should do a thorough evaluation of your volume, frequency and category of outgoing emails (transactional v/s promotional), and weigh them against your budget constraints before deciding whether to opt for a dedicated IP, or to use a shared one.
    • Monitoring your Sender Score: Sender Score is a number between 0-100 assigned to an IP that denotes its reputation.You can check your sender score by visiting A high score means a good reputation- translating in better overall email deliverability and vice versa. Sender score is an overarching data point that is influenced by many variables, including but not limited to:
      • Spam Complaints
      • Bounces or Undelivered emails
      • Getting caught is Spam traps frequently launched by ISPs
      • Email volume
      • Poor email content
    • Verify Domain Existence: If the email contains links to domains that throw an error upon visiting, Email Service Providers will notice this error and might put your account on watch for malicious behavior or even blacklist it.
  • While Creating Emails

    • Formatting mistakes like
      • Using ALL CAPS- especially in the Subject line
      • Too many punctuation marks like ‘?’, ‘!’ etc.
      • Too many colors in your email
      • Using large font sizes (bigger than 10pt or 12pt)
    • Image-to-text ratio: Spam filters can classify emails containing a large number of images or a single large image as Spam since spammers often display information through images to avoid their content from being read and flagged by the email application. To avoid such situations, we should ensure that there are not too many images, or a few large images with too little text in the email.
    • Using URL Shorteners - Spammers often use URL shorteners to bypass spam filters. As a response, many URL shorteners have been blacklisted by email clients and using them can result in your emails get blacklisted as well.
    • Email Content - Software applications like Gmail are equipped to analyze the content of your email and decide whether the email is fit to be shown in their inbox, or to be marked into other folders like Social or Promotions, or even directly be sent to the Spam folder. Further, such classifications by email clients are noticed by ISPs as well, and can potentially result in a negative impact on your reputation as a sender. To avoid this, you need to avoid poor email-writing practices that trigger Spam filters. Some of these include:
      • Keep the mailing list updated: When your account is found to be sending emails to addresses that are no longer functional, it increases your bounce rate and Internet Service Providers tend to view this as a sign that your account is spamming users instead of sending genuine emails to a legitimate audience. This can impact your reputation negatively. The MoEngage platform ensures that email accounts that report a bounce, or trigger an Unsubscribe or mark the email as Spam are removed from the mailing list for the next time. In addition, you can also ensure that the emails uploaded into MoEngage are sanitized.
      • Provide an Unsubscribe link: Apart from causing a poor user experience, Marketing emails without an option for recipients to opt out of a mailing list are also perceived by ESPs and Email Clients as spam and can get the sender blacklisted.

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