Should I use the same or different subdomains for multiple ESPs?
Summary
What email marketers say8Marketer opinions
Email marketer from GMass explains that using multiple domains to improve your deliverability could improve your results, and having a separate domain for transactional and marketing emails to improve trust.
Email marketer from Reddit shares the opinion that using separate subdomains provides a level of isolation and control. If one subdomain gets blacklisted, it won't necessarily impact the others. This is especially important when using multiple ESPs with potentially varying sending practices.
Email marketer from Mailjet Blog explains that using dedicated subdomains for each ESP helps isolate sending reputations. If one ESP experiences deliverability issues, it's less likely to affect the reputation of your other ESPs. This also allows for more granular tracking and management of each ESP's performance.
Email marketer from SparkPost Blog shares that segmenting sending domains by message type (transactional vs. marketing) and/or ESP is a recommended approach. This allows for better reputation management and isolation of deliverability issues.
Email marketer from SendGrid Blog recommends using subdomains to organize email sending and protect your primary domain's reputation. This allows you to isolate any deliverability problems to a specific subdomain, preventing them from affecting your main domain. It does not specify about multiple ESP's but can be implied to apply.
Email marketer from EmailDeliverability.com explains that you could risk having your IP shared when using multiple ESP's and having different subdomains could allow you to isolate your sending reputation.
Email marketer from Litmus recommends a segmented approach to email infrastructure, including subdomains. This helps with tracking, deliverability monitoring, and overall management, particularly when dealing with diverse email streams from different ESPs.
Email marketer from Stack Overflow explains that having different subdomains for different email purposes (marketing, transactional etc.) or different ESPs prevents having the risk of one negatively affecting others' deliverability.
What the experts say5Expert opinions
Expert from Spam Resource explains that using different subdomains for each ESP allows for better isolation of sending reputations. If one ESP has deliverability problems, it's less likely to negatively impact the reputation of the other ESPs.
Expert from Email Geeks explains that it is desirable for the rua/ruf mailto to be different than the from: email used. Reply emails should go to a human, while DMARC reports should go to automation.
Expert from Word to the Wise, Laura Atkins, answers question about testing email sending variations. She explains that using subdomain variations is useful for experimenting to measure if it effects deliverability. Useful for measuring impact of using different ESPs.
Expert from Email Geeks explains the importance of having mail authenticated via both SPF and DKIM, and having the domains used for authentication be "DMARC aligned" with the From: header. They also mention that while DMARC alignment is a decent goal, it's not essential, nor is it essential to have different subdomains to achieve it.
Expert from Email Geeks shares that there are reasons to use the same subdomains across multiple ESPs, and reasons not to, mostly tied to the reputation of the mail streams being more strongly shared.
What the documentation says5Technical articles
Documentation from Cloudflare details the DNS configuration needed for managing subdomains. It shows how to configure SPF, DKIM and DMARC records.
Documentation from DMARC.org describes how DMARC policies can be applied to subdomains. Using separate subdomains can allow you to implement different DMARC policies for different types of email traffic.
Documentation from Microsoft explains how to configure SPF records for subdomains. It highlights the importance of properly authenticating each subdomain to ensure deliverability and prevent spoofing. While not specific to multiple ESPs, this emphasizes a crucial technical aspect.
Documentation from Google Workspace Admin Help explains how to set up subdomains for email routing within Google Workspace. While focused on Google's ecosystem, it illustrates the technical feasibility and management aspects of using multiple subdomains for email.
Documentation from RFC highlights the importance of a consistent and identifiable sender ID. While not directly addressing multiple ESPs, it emphasizes that a clear and trustworthy sender domain (which subdomains contribute to) builds recipient trust and improves deliverability.