Why they should not share a reputation.
THE PRINCIPLE
If a marketing campaign generates complaints, that should not prevent order confirmations arriving.
HOW TO SEPARATE THEM
Marketing through your marketing platform Transactional through SMTP, either from a hosting mailbox or a dedicated transactional service
Some services offer both with separate sending reputations. Check whether yours does.
USING DIFFERENT SUBDOMAINS
Larger senders use a subdomain for marketing, keeping the main domain's reputation for transactional mail.
That is more configuration than most small businesses need, and it is the principle behind the separation.
WHAT MATTERS MOST
That transactional mail arrives reliably.
A customer who does not receive an order confirmation contacts you, or assumes the order failed.
WHAT TO CHECK
Send a test of each kind and confirm both authenticate correctly.
cPanel > Track Delivery shows what happened to messages sent from your account.
FOR A SMALL BUSINESS
The practical minimum: marketing through a platform, transactional through SMTP from your domain.
That separation alone covers most of the risk.
