The SMTP relay protocol allows email messages to be transferred from one SMTP server to another on their way to their final destination. These SMTP servers are sometimes called Mail Transfer Agents (MTA). They transfer emails from the sender’s computer to the recipient.
SMTP relay was created in 1982, and it has become a widely used standard today; if you send an email to someone who is in a different domain or who is far from you, the email won’t just get to them directly; it will go from one SMTP server to another until it gets to your recipients SMTP server before your recipient can receive the email and this process is made possible through SMTP relays.
Although this seems like a long process, it happens in seconds, and neither the sender nor the receiver has to worry about any of these activities because they are done automatically in the background.
What is an Open Relay?
An open relay is a server that allows anyone on the internet to send emails to anyone, regardless of whether the sender’s or receiver’s IP address is authorised. An open relay differs from the SMTP relay protocol because it doesn’t have a proper authentication mechanism. So, it was a security risk as spammers and malware distributors constantly exploited it.
However, it is no longer in practice today as nearly all open relay systems have been shut down, and SMTP authentication is now required before email clients can use any SMTP server to send emails.
Why is SMTP Relay Important?
First, SMTP relay enables you to reach a wider audience with email marketing campaigns regardless of their providers and location. Second, monitoring SMTP response codes can give you insight into your delivery rates and campaign success and help you identify delivery issues that need fixing.
In addition, if an email cannot be delivered for any reason, the receiver’s SMTP server will send a bounce notification back to you as the sender so you can track email deliveries and bounce messages through the SMTP relay protocol. This allows you to clean and maintain your email list to improve sender reputation and deliverability.