Why use a sending subdomain?
A sending subdomain is a separate name under your main domain, for example news.yourcompany.com or mail.yourcompany.com, from which you send your automated or commercial email instead of sending it straight from yourcompany.com. You use one because reputation is partly tied to the sending domain: if a campaign goes wrong, it hits the subdomain and not the mail you use every day to correspond with customers and suppliers.
Why reputation counts per domain
Receiving providers keep track, per sending domain, of how their users respond: open, ignore, delete, report as spam. That history helps decide where your next message lands. If you send everything from one domain, your quotes, your invoices and your newsletter share one and the same reputation. A single badly timed promotion to an old list then also costs you your accounting department's mail. With a subdomain, each kind of mail builds its own history, and damage stays where it belongs.
The typical set-up
Three layers, each with its own purpose:
- The main domain (yourcompany.com) for personal correspondence: mail that people write and reply to.
- A subdomain for transactional mail (for example mail.yourcompany.com) for order confirmations, password resets, invoices and notifications. Mail that has to arrive, and that is rarely reported.
- A subdomain for campaigns (for example news.yourcompany.com) for newsletters and promotions. Mail with a higher complaint risk.
That way a campaign cannot drag your order confirmations down, and a hacked contact form cannot contaminate your newsletter. What exactly the distinction between those two kinds of mail involves is explained under transactional email.
A real-world example
A wholesaler sends a monthly promotion to twenty thousand addresses and a few hundred order confirmations and invoices every day. Everything leaves from the main domain. After a promotion to a poorly maintained list, delivery drops at one large provider, and the following week customers report that invoices are landing in spam. Had the promotion gone out from news.wholesaler.com, that provider would only have penalised that subdomain and the invoices would have arrived as usual.
What it does not fix
A bad list is still a bad list. The subdomain moves the problem into a separate room, but the problem itself remains. And the reputation of your main domain still counts: providers can see that news.yourcompany.com belongs to yourcompany.com. It is a separation, not an escape. Anyone who uses a subdomain to hide spam-like behaviour quickly finds out it does not work.
What to watch
- Each subdomain needs its own SPF, DKIM and DMARC settings. Records on the main domain do not automatically apply to the subdomain. What to put in DNS per domain is explained under SPF, DKIM and DMARC.
- Each subdomain has to be warmed up separately. A new subdomain starts with no history. Switching on Monday and sending the full newsletter on Tuesday is exactly what not to do.
- Pick a name that inspires trust. "news", "mail", "info" or "shop" are recognisable. Cryptic names like "mta3" or "srv-out" look like phishing to the reader.
- The reply address can stay on the main domain. Anyone who replies to your newsletter then simply reaches your team.
- Sending platforms usually charge per sending domain. Each subdomain then counts as a domain; how that works at 2Mail is on the pricing page.
How to tell you need one
Your invoices or confirmations arrive worse in the week after every big campaign. Or the reverse: you no longer dare to send a campaign because you fear for your everyday mail. Both are the signal that two kinds of mail are sitting too close together.
When it is overkill
If you send a few hundred messages a month from one domain, and mostly personal correspondence, this separation gains you little. The extra DNS records and the warm-up cost more than they return. The separation starts to matter as soon as marketing and system mail both run serious volume, or as soon as several systems send on your behalf.
Frequently asked questions
Does the recipient see the difference?
Hardly. The sender name remains your brand; only the address behind the name changes from info@yourcompany.com to info@news.yourcompany.com. Most readers do not notice.
Can I use a completely different domain instead of a subdomain?
You can, but it is worse. A separate domain like yourcompany-news.com has no link to your brand and looks more suspicious to filters and readers alike. A subdomain inherits part of the main domain's trust.
Do I need a subdomain per application?
No. One per kind of mail is enough. Several applications that send transactional mail share the same subdomain, each with its own SMTP login so you can follow and revoke them separately.