Best for multi-tenant and agency email

Strong fit for agencies and platforms that need domains, routes, logs, and sending separation at scale.

Mature subuser model and enterprise controls, with dated ergonomics as the tradeoff.

Modern API and sub-account story for teams that want developer and client-facing surfaces together.

Servers and streams make client or app separation clean when transactional quality matters most.

Predictable SMTP relay with account structures that work for consultants and managed senders.

Unlimited users and subaccounts are listed on paid API plans, useful for reseller-style setups.

Unlimited sub-accounts help ecommerce operators separate stores or client programs.

Useful when tenant-specific notification preferences span email plus other channels.

Open-source and cloud paths for product teams building tenant-aware notification infrastructure.

MSP and reseller options make domain-authentication monitoring practical across many clients.