Glossary
Email protocol
A standard way for systems to exchange mail: SMTP to send, IMAP and POP3 to read.
ValidReach Team · Updated 2026-10-26
In practice
SMTP moves messages between servers and from clients to servers, usually on port 587 or 465 with encryption. IMAP keeps mail on the server and syncs it across devices; POP3 downloads it.
Verification and sending
A mailbox check is an SMTP conversation: the verifier asks the receiving server whether it would accept a recipient, without sending a message.