𝗛𝗼𝘄 𝗘𝗺𝗮𝗶𝗹 𝗩𝗲𝗿𝗶𝗳𝗶𝗰𝗮𝘁𝗶𝗼𝗻 𝗪𝗼𝗿𝗸𝘀
Email verification is a stack of checks. Each layer costs more and provides different data. You should choose the right layer to avoid overpaying.
Layer 1: Syntax Checks This check asks if the string looks like an email. It uses regex to find errors like extra spaces or missing symbols. It is fast and free. However, it is weak. A fake address like nobody@asdf.asdf passes this test.
Layer 2: MX Record Checks This check looks at the domain. Every domain that accepts mail has MX records in its DNS. A quick lookup tells you if these records exist. If a domain has no MX records, it cannot receive mail. This step removes many fake domains.
Layer 3: SMTP Checks This is the deepest level. The system connects to the mail server to ask if the specific mailbox exists. It does not send a real message. This layer has flaws:
- It is slow because it requires a live connection.
- Many servers say yes to every request.
- Providers often block these probes.
SMTP checks work best for cleaning old lists. They offer little value for new signups.
Other useful signals:
- Disposable detection: identifies throwaway email providers.
- Role detection: identifies addresses like info@ or admin@.
- Typo suggestions: catches mistakes like gmial.com.
- Deliverability scores: provides a single number for easy sorting.
The best strategy for signup forms: Use syntax checks, MX checks, and heuristics. This catches most bad addresses quickly and cheaply. Avoid SMTP probing for signups. Save SMTP for cleaning stale bulk lists.
Ask what you need to prevent before you choose a tool.
Source: https://dev.to/atek/how-email-verification-works-syntax-mx-and-smtp-explained-4k2n