SMTP relay services are third-party providers that assist in the delivery of email messages from the sender to the recipient's email server. These services act as intermediaries, improving the reliability and deliverability of email communications.
SMTP relay services offer several advantages for businesses and organizations. First, they provide a scalable infrastructure capable of handling large volumes of outgoing email traffic. This ensures that emails are sent promptly and efficiently, even during peak periods.
Source-https://smtpget.com/smtp-service-provider/