Supported mail provider backends.
'log'— writes each message to the resolvedILogger(and an optional sink); the zero-dependency default, works on every runtime including Cloudflare Workers. For testing/local development.'smtp'— SMTP vianodemailer(injected transport or lazynpm:import); Node/Deno/Bun only (raw sockets, not available on Workers).'ses'— AWS Simple Email Service via@aws-sdk/client-sesv2(injected client or lazynpm:import).'sendgrid'— SendGrid v3 HTTP API over web-standardfetch(zero-dependency, Workers-portable).