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SMTP Relay vs. SMTP Server: Understanding the Differences

An SMTP relay can help improve the deliverability of your email campaigns. Learn how SMTP email relays are different from SMTP servers and their benefits.

Since emailing has been a service for such a long time, many people using it take it for granted. In fact, email was available to most people before other internet services, and it's a technology that's easily accepted because of email's similarity to snail mail. This makes it popular for business and personal communication.

Email communication has several benefits, including:

  • A quick way to send a message privately or to a group.
  • Easily implemented within a business.
  • Easy to understand format for most people even if they don't typically spend time online.
  • Still one of the top ways to communicate with customers, work teams, or an entire company.
  • Used by all businesses, including enterprises, small organizations, and self-employed individuals.
  • Inexpensive to use for marketing compared to traditional mail, digital advertising, and other channels.

Effectiveness depends on your industry, with open rates ranging from about 15 to 22% and click rates at approximately 2 to 5%. These considerations are important in any email marketing strategy. Comparing your rates vs. your industry's rates can help you plan goals to improve the effectiveness of your campaigns.

Even though email is a long-established communication channel, the development of technology for email has continued because of the increasing need for privacy, security, and speed to accommodate more data like videos, images, and links.

One of the biggest advantages for email users is that you don't have to wait for the postman to deliver your mail. Email technology works 24/7, so you can get messages any time of day or night. This technology allows emails to pass between SMTP relay servers from the email sender to the recipient. Let's discuss how that works.

What is an SMTP relay?

Before diving into what an SMTP relay is, it's important to understand the protocol that powers it. SMTP is an acronym for Simple Mail Transfer Protocol, and it's utilized to deliver outgoing mail. However, it isn't capable of accepting incoming emails.

At its core, an SMTP relay is the movement of emails from one email server to another, enabling you to get your message to the right recipient. These servers are designated Mail Transfer Agents (MTAs), which is software that transmits your messages to your recipient.

An SMTP relay is the email version of mail transport vehicles, like trucks and planes that get snail mail from one place to another. SMTP is the software that "picks up" the email and sends it to the SMTP for the recipient. Then the recipient's SMTP receives the message and delivers it to the recipient.

What is an open relay?

When email technology was first developed, open relays were the standard setting. This setting allows anyone to send emails and doesn't make any distinction between spam and a valid email. Because this resulted in massive spam and phishing problems, most organizations no longer use open relays. Hackers continue to get smarter, prioritizing email security for individuals and businesses.

Key differences between SMTP relay vs. SMTP server

The terminology used to describe SMTP relay technology can confuse users because of similar terms. Another reason is that sometimes the terms are used incorrectly. This is true when discussing SMTP relay and SMTP servers.

An SMTP server is a software application or computer that has the job of sending emails. The terms SMTP server and SMTP relay server are often interchanged to refer to the definition of email relay servers that messages move between. When using this definition, SMTP server and SMTP relay are the same thing.

However, used correctly, SMTP servers refer to computers that transfer email messages. Then SMTP relays describe the process of moving emails from one computer to another. It's easy to see how these can be misused.

Benefits of using SMTP relay

Whenever anyone sends an email to another domain (different from their own), they use an SMTP relay. Your business can use internal SMTP servers, but you can also use servers based in the cloud. Your internet service provider (ISP) can set up SMTP servers for your company. A business has to use email servers that use an exclusive domain for all the email addresses in the company.

Third-party services, like Mailchimp, can make creating and using your own domain for emails easier. There are also several other options based in the cloud that let you send business emails without utilizing your own internal server.

Benefits of SMTP relays include:

  • Sending marketing messages without using your own domain
  • Facilitating the transmission of bulk emails
  • Preventing customers from blocking your primary domain
  • Use of a secondary domain for your marketing emails
  • Better unsubscribe and opt-out features
  • Easier compliance with laws and regulations
  • Email tracking and recipient interaction tracking
  • An interface or dashboard to create, review, and publish emails
  • Assurance that emails are sent and received without an internal server

When to use an SMTP relay

Most businesses use SMTP relays to send bulk emails to internal or external recipients. Doing so prevents emails from their domain from being labeled as spam and improves delivery rates. These factors make SMTP relay services ideal for email marketing campaigns.

Preventing spam is a crucial part of an ISP service, so bulk emails from a single source have the potential to get blocked. This is especially true for any public domain, like, because anyone can use them and share an IP address. Unfortunately, this means that legitimate emails can get caught in a spam filter instead of reaching your list of recipients.

Public domains don't have access to DNS information, preventing you from instituting protocols for compliance and email authentication factors.

Public domains also have a maximum send rate per day/week/month, which can prevent you from sending necessary emails out to your contact list.

Another issue when creating your own SMTP server can be having a domain that isn't recognized automatically by servers. This is why using an SMTP relay from reputable email service providers (ESP) to send bulk emails is a good solution for any business.

How to choose an SMTP relay service

There are several SMTP relay services and providers to choose from, making it difficult to identify the best one. From free SMTP servers to paid service providers, there's a lot to think about when it comes to your SMTP mail relay.

When you're ready to choose an SMTP relay provider, there are certain factors to consider:

  • Do they have a good reputation?
  • Is their service reliable?
  • Do they have a lot of downtime?
  • What is the track record for deliverability rates for your industry?
  • What methods do they have to increase email deliverability?
  • What kind of email infrastructure do they have?
  • Is there a free trial?
  • How much does the service provider cost?
  • Do they have an affordable pricing plan?
  • Can they help you avoid spam filters?

A reliable SMTP service will keep your business compliant with authenticity, privacy, and security regulations so that you don't have to monitor them. This includes regulations in the United States, the European Union, and other countries. If you run a global business, your marketing process needs to comply with the laws of the sender and recipient country. This can become confusing because rules often change to meet new hacking issues. Staying up to date can be an entire job.

Mailchimp offers you a wide range of services and the experience of a long-term, reliable email provider with a great team to help you when needed. This way, you can ensure your marketing emails are delivered quickly and efficiently.

Improve deliverability with SMTP relays

Understanding how an SMTP relay and SMTP server can benefit your company's revenue streams, help your marketing team discover new customers, and allow you to keep in touch with existing customers is essential. This knowledge can affect your profitability and ability to continue interacting with customers at every stage of the buying cycle.

The bottom line is that you can improve email deliverability with an SMTP service, making reaching out to people easier for your business. Mailchimp’s digital marketing tools can help ensure your marketing campaigns are successful. It's easy to see why many companies choose Mailchimp as an SMTP to deliver emails to customers, prospects, employees, and stakeholders.

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