Local-first processing
Email lists and validation results remain on the device by default. Network checks contact DNS or recipient mail infrastructure only when the selected mode requires them.
RS Email Verifier
Understand list quality before you send
RS Email Verifier is a local-first desktop application that combines format checks, rules, DNS/MX lookup, and optional SMTP probing. It reports explainable valid, invalid, risky, and unknown outcomes instead of hiding uncertainty behind a single verdict.
The problem
An email can look correctly formatted and still have no mail server, belong to a disposable domain, match a high-risk pattern, or sit behind a server that refuses to reveal mailbox existence.
Sending an unreviewed list increases avoidable bounce and reputation risk. Treating every uncertain response as valid or invalid creates a different problem: false confidence.
Core value
Layered validation depth
Choose a quick local screen, confirm domain mail routing, or run a deeper SMTP probe. Use the depth appropriate to the value and risk of the list.
Explainable outcomes
Review the main reason, risk details, MX/MTA information, SMTP response category, and catch-all uncertainty.
Features
Single verification
Enter one address, choose Basic, DNS, or SMTP Pro, and review the validation stages and result.
Batch verification
Import TXT or CSV data, deduplicate locally, configure depth and workers, then start, pause, stop, filter, and export a long-running task.
Basic mode
Runs local format checks, domain extraction, role-mailbox rules, typo signals, trap keywords, disposable and blacklist data when available, local custom rules, and batch-pattern signals.
DNS mode
Adds an MX lookup. A missing MX can produce a hard invalid result; timeout or proxy failure remains unknown rather than being mislabelled as invalid.
SMTP Pro
After a usable MX is found, the verifier can perform HELO, MAIL FROM, and RCPT TO probing. A second randomized recipient probe helps identify catch-all or anti-enumeration behavior.
Proxy pool
Import and validate proxies, control whether the pool is used, and observe health. A proxy problem is a network outcome, not proof that an address is bad.
Local and official rules
Create local Block or Risky rules. Eligible Enterprise licenses can download signed official rule packages and merge their data without deleting local rules.
Reports and export
Filter results, inspect status and reason distributions, review domain and MTA patterns, calculate list quality, and export CSV data.
Workflow
- Choose validation depth.
- Verify a small sample and review the explanations.
- Import or paste the batch list.
- Confirm deduplication and task settings.
- Configure a proxy pool only if your network workflow requires it.
- Start the task and monitor speed, progress, and status counts.
- Pause or stop if results indicate a configuration problem.
- Filter risky and unknown results for review.
- Export only the result set you need.
Use cases
- Cleaning CRM or campaign lists before use
- Comparing the quality of lead sources
- Identifying malformed, disposable, or no-MX addresses
- Separating hard failures from reviewable risk
- Investigating recipient-domain and MTA patterns
Privacy and result boundaries
RS Email Verifier does not send a real message during SMTP verification and does not enter the SMTP DATA phase.
Recipient mail servers can rate-limit probes, hide mailbox existence, accept all recipients, or return temporary errors. For that reason:
- valid means the selected checks produced positive evidence;
- risky means review is recommended;
- unknown means the available evidence was inconclusive;
- no result guarantees that a person owns, reads, or will receive mail at the address.
Product relationship
Use MailFleet to deploy supported mail-server nodes and RSender to operate authorized campaigns. Moving a verifier export into another tool is a deliberate user action, not an automatic integration.
FAQ
Does Basic mode use the network?
Basic mode is designed as a local screening stage. DNS and SMTP network checks are added only in their corresponding modes.
Why can a correctly formatted address still be invalid?
Format only checks structure. The domain may not route mail, the address may match a blocking rule, or SMTP may report that the recipient does not exist.
Is a catch-all result valid?
It is uncertain. The server accepted a randomized address as well as the tested address, so RCPT behavior alone cannot confirm that specific mailbox.
Can a proxy make validation more accurate?
Not automatically. A reliable proxy can change connectivity, but a poor proxy increases timeouts and unknown results.
Discuss your list-validation workflow
Tell us your list size, validation depth, network constraints, and reporting needs.
Consult about RS Email Verifier