Many of us don’t know it but even when we’re off work, parts of the World Wide Web keep working nonstop so we can remain connected. One of those are Simple Mail Transfer Protocol (SMTP) servers that process the coming and going of emails from one outbox to an inbox. But what is an SMTP relay server? How does it work? And is it truly important?

What Is an SMTP Relay Server?

An SMTP relay server works in the background to deliver outgoing emails. It doesn’t accept incoming emails, other protocols do that. Post Office Protocol (POP) and Internet Message Access Protocol (IMAP) are the protocols that allow email retrieval from a mail server. They are, in essence, the counterpart of SMTP, which lets you send emails to a mail server.

How Does SMTP Relay Work?

This simple illustration shows how SMTP relay works. Note that the process is more complicated than this but we won’t get into that.

For our purposes, it’s enough to know that when Anna sends an email, it goes through her provider’s SMTP relay server. The SMTP relay server sends the email to Alex’s POP/IMAP relay server. And the POP/IMAP relay server finally delivers the email to Alex.

Think of it this way, the SMTP relay server is the post office where Anna drops her letter to Alex at. The POP/IMAP relay server is the postman assigned to deliver mail in Alex’s area. The letter, of course, is the email, which Alex gets when the postman leaves the letter in his mailbox.

What Is an SMTP Relay Service? Do You Need It?

If your company employs email marketing, you’ve probably heard that it subscribes to an SMTP relay service. While anyone can send emails in bulk, he/she can’t ensure that they won’t get tagged as spam. To avoid this unwanted scenario, offices employ an SMTP relay service provider (a trusted third party) that routes their bulk emails through their servers to deliver these. Large message batches like newsletters or automatic transactional emails (e.g., delivery confirmations, password resets, etc.) are some examples of the communications SMTP relay services handle.

The SMTP relay service provider ensures that your bulk emails are not categorized as spam and your company a spammer.

Why Is Using an SMTP Relay Service Important?

If you happen to work in customer service, how many times have you received complaints from customers saying you shouldn’t have disconnected their service? You calmly tell them their service was cut because they failed to pay their monthly bill. They argue that they didn’t receive the bill and so weren’t able to pay. You’re sure you sent out all the bills and think these must have ended up in their spam folder.

This situation happens when you send bulk emails from unknown or disreputable servers. Those include the servers of free email providers like Gmail, Hotmail, or Yahoo, not because they have a poor reputation, of course. It’s more due to the fact that even spammers and phishers can avail of their services. Sending bulk emails is, after all, a tactic spammers and phishers employ all the time. That said, any mail server they used recently can get flagged and all messages sent through that server afterward are automatically marked as suspicious. That is especially true if the messages you’re sending in bulk like bills and marketing communications look very similar to one another.

The problem is avoidable if you employ an SMTP relay service, though. SMTP service providers typically maintain reputable servers, ensuring none of their clients’ bulk emails end up in recipients’ spam folders.

Another bulk mail sending challenge has to do with the fact that all email providers impose hard limits on the number of messages you can send at once. If your company heavily relies on email marketing, it becomes too troublesome to get your message across to all campaign recipients in the fastest time possible.

You might think setting up your own SMTP relay server is the answer but it’s not. While that may work at first, you’re bound to suffer from the same deliverability issues again. Once the server gets flagged for sending too many emails at once, its reputation will eventually suffer. It will be tagged a spammer, too. And your all-important messages? They’re bound to end up in intended recipients’ spam folders at best.

Avoiding these hassles is the primary reason why you may need the help of established email sending providers (ESPs). These providers have built and been maintaining a good reputation for years. They have very reputable SMTP relay servers and so are bound to get your message across without a hitch. Some won’t only deliver your bulk emails, they can also give you access to mail-sending analytics to measure your success and templates that can improve your open rate.

No matter how dated you may think email is, know that 4.03 billion people worldwide use it. Even now, not even social media comes close to email’s potential reach. And as most of today’s marketing happens online, a reliable SMTP relay server is a must for most if not all companies.