Email Marketing

3 sending domain best practices

Maximize email deliverability with these effective sending domain practices

What do engineers and deliverability analysts have in common? They both understand that you can’t build something great without a strong foundation. How does this relate back to email? A key to a successful email campaign is getting your email in front of subscribers. How do you accomplish that? Well let’s start with your foundation – a properly configured sending domain.

Whether you are in the process of migrating to a new ESP or evaluating your current domain’s set up, determining the proper structure for your sending domains has significant impact on the success of your email program when it comes to your sender reputation and overall email deliverability.

Sender Reputation

Your sender reputation reflects how your email program is perceived by the Mailbox Providers (ISPs), such as Gmail, Hotmail and Yahoo. A positive sender reputation will ensure your campaigns achieve strong inbox placement with your subscribers. While many factors contribute to a sender’s reputation including opt in process, user engagement and authentication, one of the root factors is how your domain and IP setup is configured.

Some of the factors that ISPs measure when determining an email sender’s reputation are:

When was the sender domain originally purchased and setup? Is it consistent across all channels?

  • Avoid purchasing a new domain and using it for email deployment – utilize your existing domain (or subdomain) where your website is hosted instead. Not only will this strengthen recipient trust and branding, but using any other domain is an easy way for a legitimate sender to get incorrectly categorized as a spammer with a poor domain reputation.  Purchase history and familiarity of existing domains with ISPs will help maintain or increase your overall brand trust and reputation.

What has the sender domain been used for to date?

  • Your sending reputation is not something that can be erased or reset easily. ISPs and blocklists often monitor your email campaigns and recipient responses for weeks, months and even years. You will want to ensure that the domain in which you are using to send to your engaged subscribers does not already have a negative reputation caused by poor sending practices.

Are your IPs dedicated or shared?

  • Your sending domain is just one piece of the puzzle. The IPs you are sending from can often hold just as much weight in the deliverability world as the sending domain in which you are using. When you are configuring the foundation of your email program evaluate whether you would like to have dedicated IPs that only you will be using or whether you will send from those IPs with other senders. Although there are pros and cons to both options, you will have to look at your mail program to determine the right fit. You will need to analyze if you will be mailing enough volume constantly to support a strong reputation on your own. If not, there are some benefits to sharing IPs, but also some risks – Your sender reputation will be impacted by the email practices of all other mailers utilizing those domains.

Is your domain properly configured, including domain alignment and proper authentication?

  • All major mailbox providers ensure that emails are properly authenticated, in order to achieve this, you must ensure that your emails are properly configured – This includes passing SPF, DKIM and DMARC policies. In addition, these protocols protect your domains’ reputation from spoofing attempts by implementing proper authentication protocols. Learn more about the power of authentication.


Domain name = recognition and trust! In an inbox full of bad actors, often it’s the sending domain the reassures recipients that your email is legitimate. We’ve all seen phishing or spoofing attempts sent from a different domain, attempting to mimic a legitimate company or brand by using similar content. Although it’s still possible to spoof a domain, if you set up proper authentication, the odds are much less likely. This reaffirms the importance of utilizing an existing domain name registered to your company (ex: as opposed to purchasing a new domain specifically for deploying your email marketing.

You can support domain recognition by adding logo (BIMI), specific color scheme and clear from name to your emails. Here are some additional resources from the Inboxable team on how you can make your emails more visible and identifiable within Gmail and other SPs’ platforms:

Mail Stream Separation

It remains a best practice to utilize a unique subdomain for varying forms of email that you send, for example promotional vs. transactional emails. Because promotional email marketing has different audiences, response rates and volumes, it can occasionally trigger deliverability challenges. It’s important to avoid those challenges from impacting critical transactional emails that need to reach your users (ex: password reset emails). The best practice for domain setup with varying mail streams should look like:  

Bottom Line

Determining your sending domains has significant impact on the success of your email launch when it comes to inbox placement rates and your sender reputation. To ensure optimal deliverability:

  • Ensure your root sending domain is consistent
  • Utilize subdomains for different types of emails you send (transactional vs marketing)
  • Protect your domains with proper authentication (SPF, DKIM, DMARC)
  • Monitor deliverability performance regularly (inboxing, bounces, engagement, reputation, spam complaints, and blocklistings)

And as always, if you need any assistance with determining the best set up for your mail program – please reach out to the Inboxable team!

Anna Tchirova
Anna Tchirova
Senior Deliverability Analyst

Anna Tchirova is a Senior Deliverability Analyst at Data Axle. She is passionate about deliverability and maintaining client-facing support for Inboxable technology and service offerings. An industry professional for over 16 years, her expertise allows her to provide clients with effective campaign strategies and efficient issue resolution in email deliverability. In her free time, she enjoys spending time with her family and friends as well as listening to podcasts and reading.