Email Verification API and Deliverability Service

Our registration form and advertising database are growing, constantly polluted with typos, dead mailboxes, and disposable addresses. Bounces damage sender reputation, and I want to filter garbage at the input stage. I'm hiring a developer to build an email verification service and deliverability assessment as a clean HTTP interface. The main task is to quickly and reliably answer for any address whether it's worth sending mail to it. This means proper syntax parsing, domain and MX record checking, and careful mailbox validation that confirms the existence of an email address without blacklisting our IP.

Beyond single checks, I need batch list cleaning. I want to upload a database, get each row processed, and download the result with a clear verdict and a numerical quality score for each record. The service should recognize disposable and temporary domains, catch-all servers, and role-based addresses like department mailboxes — they behave differently, and I want to separate them. Each response is structured JSON so we can plug it into our panel and CRM, and everything must work fast enough to embed verification right at registration without delays for the user. Keep keys and secrets out of code, document the endpoints.

This is strictly about verification and cleaning of existing lists. It's not a mailing constructor, not a template designer, and not a push notification service. If you've already built verification pipelines or anti-spam systems, show examples and explain how you handle greylisting and request limits.

— Single check: syntax, domain, MX, mailbox presence
— Detection of disposable, catch-all, and role-based addresses
— Batch list upload with verdict and score per row
— Structured JSON API with keys, limits, and documentation
— Sensible greylisting handling without false rejections