When should I use subdomains for email sending and how do they affect my reputation?

Marketer from Email Geeks shares that sharing a domain is bad, subdomain reputation is less than a domain reputation, and subdomains should be warmed.

Email marketer from SendGrid states that using subdomains can help protect your primary domain's reputation. If a subdomain's reputation is damaged due to sending practices, it won't directly impact the deliverability of emails sent from your main domain.

Email marketer from Quora says that using subdomains is beneficial when you have different departments sending emails (e.g., marketing, sales, support) so you can segment your sending reputation and makes it easier to troubleshoot deliverability issues

Email marketer from Customer.io highlights that segmenting your emails into subdomains prevents issues with one type of email from affecting the others, improving deliverability.

Email marketer from Reddit shares that using subdomains is beneficial when you have different departments sending emails (e.g., marketing, sales, support). It helps segment your sending reputation and makes it easier to troubleshoot deliverability issues.

Email marketer from Litmus states that if you're experiencing deliverability problems, using a subdomain allows you to isolate the issue and prevent it from impacting your primary domain. It also allows you to experiment with new sending practices without risking your core email reputation.

Email marketer from SparkPost explains that just like a new domain, a new subdomain needs to be 'warmed up' by gradually increasing sending volume to build a positive reputation with mailbox providers. A sudden spike in volume can negatively impact deliverability.

Email marketer from StackExchange shares that if you're sending large volumes of email, or have multiple sending sources, it's important to split these into subdomains to maintain your sender reputation.

Email marketer from Email on Acid suggests using subdomains to separate transactional and marketing emails. This isolates your transactional email reputation, ensuring critical communications aren't affected by marketing campaign issues.

Email marketer from Mailjet shares that subdomains are useful for segmenting email traffic by type (transactional, marketing, etc.) and maintaining a separate reputation for each. This isolation prevents issues with one type of email from affecting the others.

Marketer from Email Geeks explains that cousin domains are bad because they train recipients to click links that kinda/sorta mention you which is bad branding and that subdomains maintain branding.

Expert from Email Geeks explains that you will always need a subdomain for SPF alignment at ESPs which is the bounce domain, and that you may also want to think about what to use in the DKIM - do you want every provider to use your primary domain for DKIM authentication or do you want marketing to have a different subdomain from support?

Expert from Word to the Wise explains that subdomains are useful for separating different types of mail streams and their associated reputations. For instance, separating marketing from transactional email ensures that issues with marketing campaigns don't negatively impact the deliverability of important transactional messages.

Expert from Email Geeks shares that it’s sensible to make some decisions early on - and many of these decisions are more business decisions than delivery ones - they’re about maintainability and ease of use and not having to make these decisions every time you spin up a new stream - you just follow the policy doc.

Expert from Spamresource highlights that using a subdomain as a sender identity is like putting a department name on your envelope. If it gets trashed, it does not hurt other parts of the company. This is an important consideration when it comes to IP addresses.

Expert from Email Geeks suggests that if it’s working, don’t fix it, but to decide now what your approach to subdomains are, so when you bring up different mail streams or different providers in the future (as you grow) you have a sensible plan in place.

Expert from Email Geeks mentions that there isn’t one decision that’s right for every company, in terms of what subdomains to use.

Documentation from AWS shares that in terms of best practice you should separate out different IP addresses for different types of email to prevent deliverability issues. You need to make sure you also setup SPF, DKIM and DMARC properly

Documentation from Microsoft explains that sender reputation is calculated by domain, and any subdomains will contribute positively or negatively towards a domains reputation. It is best to isolate different types of sending onto different subdomains.

Documentation from Google Workspace Admin Help explains that using subdomains allows you to isolate the reputation of your marketing emails from your primary domain, protecting your core business email deliverability. It also suggests using a dedicated subdomain for bulk sending.

Documentation from RFC Editor shares that subdomains allow for more granular control over SPF and DKIM records, enabling you to specify different authentication policies for different email streams. This flexibility is key for larger organizations.