Subdomain strategy: why marketing.example.com beats [email protected]
Splitting transactional, marketing, and corporate mail across subdomains protects your most important traffic from your noisiest. Here is the layout that works.
Most companies start by sending everything from example.com — receipts, marketing newsletters, employee mail, the whole stream. It works until one of those streams misbehaves and the others start landing in spam. Subdomain separation is how you stop letting a Black Friday campaign hurt your password reset emails.
The recommended layout
| Subdomain | Use | Why |
|---|---|---|
| example.com | Employees, support replies | Personal mail, low volume, high trust |
| mail.example.com | Receipts, password resets, alerts | Critical — must always deliver |
| news.example.com | Newsletter, drip campaigns | Highest volume, highest complaint risk |
| promo.example.com | Sales/promo blasts | Isolates riskiest traffic |
How separation actually protects you
Modern receivers (Gmail especially) maintain reputation per-domain, not just per-IP. If news.example.com racks up complaints, that reputation hit stays mostly local — mail.example.com retains its standing because it's a different reputation entity. Without separation, every subdomain shares one bucket.
DNS layout for the split
| Host | Type | Value | TTL |
|---|---|---|---|
| mail.example.com | TXT | v=spf1 include:_spf.transactional-esp.com -all | 3600 |
| news.example.com | TXT | v=spf1 include:_spf.marketing-esp.com -all | 3600 |
| selector1._domainkey.mail.example.com | TXT | v=DKIM1; k=rsa; p=MIIBIjANBg... | 3600 |
| selector1._domainkey.news.example.com | TXT | v=DKIM1; k=rsa; p=MIIBIjANBg... | 3600 |
| _dmarc.example.com | TXT | v=DMARC1; p=quarantine; rua=mailto:[email protected] | 3600 |
When to migrate
- Stand up the new subdomain with DNS, SPF, DKIM, and a warming plan.
- Send a test cohort (1-5K most-engaged users) for 2 weeks.
- Gradually shift volume over 4-6 weeks while monitoring deliverability on both old and new.
- Once new is at full volume, announce the change in a normal email so users see the new From: domain in context.
- Keep the old domain warm with low-volume corporate mail; don't let it go silent.
Frequently asked questions
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