What’s the difference between subdomain vs sub-brand isolation?

Subdomain isolation:

• Different subdomains under same root (marketing.tidalmail.com)
• Maintains brand connection
• Partial reputation isolation
• Easier for recipients to recognize

Sub-brand isolation:

• Completely different domains (tidalupdates.com)
• Maximum reputation isolation
• No inheritance from main brand
• Requires separate warmup
• Recipients may not recognize relationship

When to use sub-brand:

• Need complete isolation (cold outreach)
• Main domain is severely damaged
• Different business unit with own identity
• Sub-brand is stronger isolation but loses brand continuity.

Subsidiary company versus company division. Different levels of separation from parent.