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Good data and loyal subscribers are the foundation of the success of your email program. This and following the industry best practices will help you to build a solid sender domain reputation. But does the sender reputation differ for various types of emails? 

It seems it does! 

Email is a powerful channel when your messages are delivered to the inboxes of your subscribers. High engagement metrics will help you to achieve your goals, so you will have to make sure you control your sender reputation by splitting the sender subdomains according to the type of email you send.  


A more in-depth explanation 

Let's define the two most common types of emails  

What makes a message transactional or marketing? 

Transactional emails are messages, initiated by a user. They are usually automated mail-streams, triggered by actions of a user on a website or in a mobile app.
Common examples for transactional emails are payment confirmations, electronic invoices, registration confirmations, password recovery emails, subscription confirmation (double opt-in, confirmed opt-in).

These messages are expected by the recipient and should be delivered in a short period of time. 

Typically, transactional emails have higher engagement.  

Marketing emails, informational or promotional, are characterized by the fact that they are usually sent in batches, these are mass mailings with interesting and useful information for subscribers, used as a tool to warm up the interest to the product, demonstrate its benefits and push to purchase. Common examples for marketing emails are selected recommendations, reviews, discounts and sales, updates, announcements. 

These messages are permission based and are usually not time-sensitive, typically show less engagement compared to transactional ones. 

Phewww! Let’s get to subdomains now… 


What is an address, a domain, and a subdomain? 

This is how a typical email address looks like: 


     info@ is the user part of your email address, it defines the mailbox and can be anything. Using no-reply addresses is not recommended though (read more). is your business domain, also called an organizational domain. It is used for corporate internal and external communications and is not recommended to be used for your email program. is the subdomain you create for a certain type of emails and use in your email program. 


What does it mean to separate transactional and marketing emails? 

Separation can happen on 3 levels: 

  1. Different sender addresses in one sender subdomain for transactional and for marketing emails 

  1. Different sender subdomains for different types of emails for transactional and for marketing 

  1. Separate sending infrastructure for transactional and marketing emails, including sender subdomains and IPs.

Gmail for example recommends the first two options in their bulk-mail guidelines. Yahoo mentions the third option. 

It is not recommended to define a separate subdomain, for sending fewer than 40-50,000 emails per month. Achieving a sender reputation is difficult with a separate subdomain, if you send emails below this monthly limit. 


What are the benefits of separating the sender subdomains? 


Transactional emails typically show a higher percentage of opens and clicks. On the one hand, having them on the same subdomain with marketing emails may help to maintain the reputation of your marketing emails. On the other hand, you do not want the reputation of your ad hoc campaigns to overwhelm the reputation of the transactional emails and negatively affect the deliverability of your business-critical communications.  

Naturally, transactional emails have a higher rate of invalid/incorrect addresses or spam trap hits. However, most mailbox providers treat a transactional sender address with a more lenient filtering, since some bad hits are inevitable for such emails as double opt-in confirmations or password resets. You lose the benefit of more moderate filtering rules when sending everything from one address or subdomain.  

By separating transactional and marketing subdomains, you make sure that these types of emails build their own reputation and do not explicitly affect each other.  


Marketing emails are usually sent to thousands of subscribers. Generating, processing, and sending the load takes time and resources. Using the same setup for all types of emails may delay time-critical emails. Password resets may be queued while a big ad hoc campaign is being sent. Separating transactional subdomain can help to improve delivery speed and thus user experience and satisfaction. 


Ad-hoc campaigns may hit the wrong audience and get the sender blocked. Transactional campaigns may fall victim to a list-bombing attack. You can benefit from separating those and optimize and fix each stream without affecting the other. 


P.S. The discussed above is not a silver bullet. You should keep in mind that some mailbox providers may aggregate the reputation across all your subdomains, so if marketing reputation and strategy leaves much to be desired, it is most likely to affect all the emails of your brand. 


What’s next? 

Please leave feedback below and/or hit the “like” button to show this type of content is useful. 

You can ask questions and provide suggestions for helpful email deliverability topics in the Q&A area Q&A – SAP Emarsys Email Deliverability. 

And if you’d like to find out more SAP Emarsys, you can visit the community page: SAP Emarsys CX.