SMTP email verification: checking a mailbox without sending
SMTP verification checks whether a mailbox exists by starting an email delivery with the receiving server and stopping before any message is sent.
SMTP is the protocol mail servers use to hand messages to each other. A delivery starts with a short conversation: the sender introduces itself, says who the message is from (MAIL FROM) and who it is for (RCPT TO). The receiving server answers the recipient line with a code: 250 if it accepts the mailbox, 550 if the mailbox does not exist.
Verification stops right there, before the DATA step where the message itself would be sent. The recipient is never contacted.
It has limits. Catch-all domains answer 250 to every address, some servers answer slowly or ask to try later (greylisting), and many networks block outgoing connections on port 25, which SMTP uses.
With Easy Email Verification
This is the mailbox check behind every Easy Email Verification result. The full conversation, step by step, is in how to verify an email address without sending an email.
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Related
- MX record: An MX (mail exchanger) record is a DNS entry that names the server that receives email for a domain.
- Email validation vs email verification: Email validation checks that an address is written correctly. Email verification goes further and asks the receiving mail server whether the mailbox exists.
- accepted_email: The receiving SMTP server accepted the mailbox.
- temporarily_blocked: The mail server greylisted the check: it asked to try again later.
- All glossary terms