SMTP verification works through a series of steps:
DNS Lookup: The process begins with a DNS lookup to obtain the MX (Mail Exchange) records of the recipient's domain. SMTP Connection: A connection is established with the recipient's SMTP server using the information obtained from the MX records. Address Validation: The server attempts to validate the email address by sending a simulated email request. The server responds with a code indicating whether the email address is valid or invalid.