What is subdomain isolation?

Subdomain isolation uses different subdomains for different email purposes:

Structure example:

marketing.tidalmail.com - promotional campaigns

transactional.tidalmail.com - receipts, confirmations

alerts.tidalmail.com - system notifications

Benefits:

Marketing problems do not affect transactional delivery

Different warmup and volume per stream

Clearer reputation monitoring per purpose

Setup requirements:

DNS records for each subdomain

SPF, DKIM, DMARC per subdomain

ESP configuration for multiple sending domains

Management:

Monitor each subdomain separately

Different sending practices per purpose

Maintain authentication for all

Separate ships for different cargo types. Each builds its own reputation.