Everything you need to know about using subdomains for email

What is a subdomain?

A subdomain is a part of a domain name. You will undoubtedly have encountered this in daily life – usually via websites of large companies – but the attentive reader will also have seen them appear more and more frequently in their mailbox. More and more marketing and transactional emails are nowadays sent via subdomains.

Subdomains are often used to link a 'new website' to an existing website or to make a certain part easily accessible.

For example, Flexmail uses the subdomain app.flexmail.eu for the application, nl.support.flexmail.eu for our manual and the traffic of our API runs over api.flexmail.eu. The subdomain is therefore related to your main domain, but inbox and internet service providers treat them individually.

You can deploy subdomains in a similar way for your email traffic:

Why would I use a subdomain for email?

Aren't they all emails from my company? The reality is, however, that you have different email streams running for different teams and different purposes. That's a lot of eggs in the same basket. So it can be useful to split those eggs.

Using a subdomain to send (certain) emails also brings a number of advantages. Below we go through them one by one:

1. Separating different types of emails

When you send different types of emails - such as personalized (or internal) emails, marketing emails and transactional emails - you can use subdomains to easily keep these different types separated from each other.

Some practical examples:

• For daily communication within the company or organization you use the main domain: `firstname.lastname@mycompany.com`
• For marketing campaigns sent to the recipients of your newsletter you use:`newsletter@marketing.mycompany.com`
• For informative campaigns sent to a press list you use: `info@press.mycompany.com`
• For transactional emails sent in function of orders via your webshop you use: `info@orders.mycompany.com`
• For transactional emails sent in function of account actions (such as a password reset) you use: `system@accounts.mycompany.com`

2. Protection of the sender reputation of your (main) domain

Having and maintaining a good sender reputation is of great importance to ensure that your emails always land in the inbox of your recipients.

When all your emails are sent via the same main domain, there is a risk that an error when sending one campaign (for example when sending an activation campaign from the marketing team) also has a negative influence on the deliverability of other, possibly more critical emails.

Subdomains can build their own sender reputation, allowing you to separate different types of email traffic from each other. This can help to limit risks and enable targeted monitoring. Do keep in mind that providers can look at patterns in the domain hierarchy and that reputations can 'seep through' from and to the root domain.

3. Easy detection and resolution of deliverability problems

If you maximize your commitment to authentication and use DMARC, you get reports that help you quickly detect problems with email delivery.

The use of subdomains can give you another helping hand in quickly localizing the origin of the problem and effectively resolving it, because you also have a better overview here.

In exceptional cases where a specific email stream has suffered serious reputation damage, deploying a new subdomain can be part of a recovery strategy. Note: only if the underlying cause has been addressed can this be effective.

Can't I just work with different senders or domains?

Like `marketing@yourcompany.com` and `orders@yourcompany.com`?

When you choose a different sender with the same domain, it is for the recipient clearer where the message came from or for what purpose it was sent, but for the email service providers all those emails are still from the same source and therefore in their eyes also have a shared reputation.

You would then think that sending via a completely separate domain could be a solution, because in that way the domain does have its own reputation, but that hides other risks such as confusion and a lack of trust.

If you normally send all emails from `@yourcompany.com` and suddenly also send emails from `@yourcompany-accounts.com`, the latter will more quickly arouse suspicion, because this could just as well be an attempt at phishing.

If you send from `@accounts.yourcompany.com` instead, you have the trust and recognizability of your own domain and the extra clarity that the subdomain provides.

How do I start with subdomains for email?

Isn't that something for large companies with their own IT team? Actually, setting up subdomains is not that difficult. If you don't have your own technical team, your hosting provider (and their associated support team) can also help you with that. If you take your domain name from our friends at Combell, for example, you are entitled to an unlimited number of subdomains.

You mainly need to determine for yourself what your communication streams look like, and how you want to split up your subdomains:

1. Determine naming

A subdomain may consist of a maximum of 63 characters and the total domain may not be longer than 255 characters. Or in other words: actually only your own imagination limits the naming of the subdomains you use.

Nevertheless, you would do well to think in advance about what email streams you have (or think you will have in the future) and in what way you would like to divide these. So first map that out throughout your organization.

In the best case, the name of a subdomain provides extra clarity, without distracting from your actual domain name or brand.

Need inspiration for your strategy?
In this article we help you step by step determine your sender details. You can also easily apply this approach to your subdomains.

2. Create and set up your subdomain(s)

Now that you have chosen the naming of your subdomain(s), you need to create these subdomain(s) at the place where your main domain is registered.

How exactly this works (and whether costs are involved) depends on your provider and the services you take from them.

If you need help with the setup, you should consult the help documentation of your hosting provider or contact their support department.

Make sure that the email addresses on the subdomain from which you want to be able to send can receive emails, so that you can validate them for use in Flexmail.

3. Add authentication

Because each subdomain stands on its own, the necessary authentication records must also be added: an SPF and DKIM record and a DMARC policy.

After you have added the desired sender address of the subdomain in Flexmail, you can create a DKIM key and generate an authentication report after the validation of the email address. You then also add these records to the DNS records of your subdomain.

Make sure that your authentication is tip-top in order before you switch to a new (sub)domain to send with.

Looking for more background information?
In this article we go through all the different components of authentication in detail.

4. Build the reputation of the (sub)domain

When you send your campaigns via Flexmail, you already benefit from our good infrastructure, but this is only part of the whole puzzle.

It is therefore advisable to gradually increase the amount of emails you send via the new subdomain during the first 30 - 90 days that you use the domain.

You yourself have an impact on the reputation of your company by working hard on relevance. That's about being consistent, good segmentation, warm contacts and content tailored to your target group.

Examples of subdomains from practice

Are you curious how others approach this in their email communication? Below a small selection from the emails of a number of well-known players:

Marketing

• info@marketing.bol.com
• info@mail.disneyplus.com
• info@mail.nintendo-europe.com
• info@insideapple.apple.com
• info@vip.dominos.be
• luminews@marketing.luminus.be
• vrt@em.vrt.be

Transactional

• no-reply@accounts.google.com
• account-security-noreply@accountprotection.microsoft.com
• no-reply@accounts.nintendo.com
• no_reply@email.apple.com
• notificatie@edm.postnl.nl
• luminus.info@communication.luminus.be
• info@comm.telenet.be
• points@connect.takeaway.com

In conclusion

As you can see, subdomains bring very useful advantages for sending emails. The initial setup requires some work and patience. But once everything is in place, you have a robust sending method. This can much better handle the challenges of bulk email sending.

Subdomains are in short a very good addition to your toolset that you certainly should not leave unused.

Need help setting up subdomains?

Our team of email experts is ready to guide you personally. Contact usfor advice tailored to your situation.