Email validation guides

Cache detect results by normalized address with per-flag TTLs. Never cache timeouts. SMTP valid/invalid/unknown tables do not apply.

Validation and verification are vendor words, not IETF terms. Split the work into syntax, classification, and SMTP mailbox pings, then buy only the jobs you need.

Block, warn, or route Gmail and other freemail with public_domain. Do not treat Workspace, Hide My Email, or disposables as the same signal.

Fail open when the checker is down. Fail closed on disposable true. Set a client timeout that matches classification, not SMTP.

Block, allow, or confirm role-based emails by product job. Combine role_address with disposable checks, and add a team-invite path instead of a dead-end error.

Gmail dots and user+tag@ aliases create duplicate accounts. Use EmailGuard’s normalized and subaddressing fields to dedupe without blocking legitimate tags.