Subdomain or root domain

You can verify the root domain (acme.com) or a subdomain (mail.acme.com, updates.acme.com). Once a domain is verified, you can also send from its subdomains, so verifying the root covers both. A domain can be verified by only one usend organization at a time.

#Why subdomains

Reputation follows the domain in the From address. Separate subdomains keep the types of mail from affecting each other:

If a campaign causes complaints, only news.acme.com suffers. Password resets keep arriving.

#Reasons to use the root

• Short, trusted addresses ([email protected]).
• A single set of DNS records to manage.
• Small senders with a single type of mail, where separation brings little.

#Practical guidance

• Separate marketing from transactional. This is the one split that nearly always pays off.
• Do not send from the same address people use for their mailbox. Mailbox providers expect a human sender there, and your employees' own mail shares the reputation.
• Add each subdomain you plan to send from as its own domain if you want its own records, tracking settings and API-key restriction. A sending_access key can be limited to one domain.
• Mind your plan's domain limit. Each domain counts: see Account quotas and limits. A verified root domain already lets you send from its subdomains without adding them.
• Receiving: an MX record on a name takes all mail for that name. Use a dedicated subdomain (for example inbound.acme.com) for receiving, not the root of a domain with mailboxes.

#DMARC across subdomains

A DMARC policy on the root applies to its subdomains unless they publish their own. Subdomains verified in usend sign with their own DKIM key and align in relaxed mode. See DMARC.

#Changing later

Switching From addresses means a new reputation for the new domain: warm it up while the old one keeps working.