The Dedicated Sending Domain: Why mail.yourbrand.com Is Non-Negotiable

When you first set up Klaviyo, it sends emails from a shared sending infrastructure. Your emails go out alongside thousands of other brands, and your sender reputation is partially tied to theirs. For small lists and early-stage brands, this is fine. But as your email program scales, sending from your root domain without dedicated infrastructure introduces a risk most brands don't think about until it's too late.

The risk is simple: your marketing email reputation directly affects your transactional email delivery. Order confirmations, shipping notifications, password resets — they all come from the same domain. If your marketing emails generate complaints or deliverability issues, Gmail doesn't distinguish between your promotional campaigns and your order confirmation. Both suffer.

A dedicated sending subdomain solves this by isolating your marketing email reputation from your root domain. Instead of sending from yourstore.com, you send marketing emails from mail.yourstore.com. The subdomain builds its own sender reputation based solely on your marketing email behavior, while your root domain stays clean for transactional communications.

Setting this up in Klaviyo requires adding DNS records to your domain registrar. The process takes 15-30 minutes of configuration and up to 48 hours for DNS propagation. In Klaviyo, go to Settings > Email > Domains and follow the dedicated sending domain setup. You'll add CNAME records that point your subdomain to Klaviyo's sending infrastructure.

The naming convention matters less than consistency. Most brands use mail.yourbrand.com or send.yourbrand.com. Some use em.yourbrand.com or email.yourbrand.com. Pick one that's clean and stick with it. Avoid anything that looks suspicious to inbox providers — marketing.yourbrand.com or promo.yourbrand.com can trigger spam filters simply because the subdomain name contains promotional language.

Once the dedicated subdomain is live, there's an important consideration: it starts with zero reputation. Gmail, Yahoo, and Outlook don't know this subdomain yet. If you immediately start sending high-volume campaigns, the lack of established reputation can trigger spam filtering. This is where the warm-up process becomes critical.

The warm-up means starting with small volumes to your most engaged subscribers and gradually increasing over 2-4 weeks. Week one might mean sending to your Engaged 14-day segment only. Week two expands to Engaged 30. By week three or four, you're at full sending capacity with established positive reputation.

Brands that skip the warm-up — setting up a new dedicated domain on Monday and blasting 50,000 emails on Tuesday — almost always see poor inbox placement in the first week. Gmail throttles unknown senders aggressively, and recovering from a bad first impression takes longer than doing the warm-up properly.

There's a common question about whether the dedicated sending domain should match the "From" address the subscriber sees. The answer is that these are different things. The sending domain is the technical infrastructure — it's what mail servers use for authentication. The "From" address is what the subscriber sees in their inbox. You can send from mail.yourstore.com at the infrastructure level while showing hello@yourstore.com as the From address. Klaviyo handles this separation automatically.

Another consideration is reply handling. When subscribers reply to your marketing emails (and some will, especially to well-crafted personal-style emails), those replies should go somewhere useful. Set your reply-to address to a monitored inbox. Some brands use a dedicated inbox like replies@yourstore.com that gets checked regularly. Ignoring replies is a missed opportunity for customer feedback and engagement.

For brands running multiple Shopify stores or multiple brands from the same Klaviyo account, each brand should have its own dedicated sending subdomain. Cross-contamination between brand reputations is a real risk when multiple brands share sending infrastructure.

The time to set this up is before you have deliverability problems, not after. Retroactively moving to a dedicated subdomain when your root domain reputation is already damaged means you're starting the new subdomain from scratch anyway, but now you also need to repair the root domain for transactional emails. Do it early, do it once, and your email infrastructure is built on a solid foundation.