How can using subdomains help isolate reputation issues?

Reputation separation:

• marketing.tidalmail.com can have different reputation than tidalmail.com
• Problems in one do not necessarily contaminate the other
• Allows different sending practices per stream

Use cases:

• Marketing on subdomain, transactional on root
• Different subdomains for different message types
• Testing new practices on isolated subdomain

Limitations:

• Not complete isolation (some reputation linkage)
• Severe root domain issues may affect subdomains
• Requires proper authentication setup per subdomain

Implementation:

• Set up SPF, DKIM, DMARC for each subdomain
• Use appropriate subdomains in From addresses
• Configure ESP to send from correct subdomain
• Separate divisions of the company with separate reputations.