Cloud-based SMTP, Technical

SMTP Relay Services Basics

Aleksandra Duło, 30 March 2023


SMTP (Simple Mail Transfer Protocol) relay is the backbone of secure and reliable email delivery. It provides a secure bridge between an email sender and the recipient’s mail server, allowing the messages to be securely transmitted over the Internet. This way, SMTP relays ensure that emails are delivered as expected and in a timely manner.

SMTP relay services are provided by a variety of companies, ranging from small to large email hosting providers. These services are typically offered as part of an email hosting package but can also be purchased separately. The email service providers will usually give you access to a web-based interface where users can configure their SMTP settings and manage their email accounts.

While it may all sound complicated, it is quite simple to understand once you break down the topic. In this article, we’ll explain the basics of SMTP relay services and how they work. We’ll also provide some tips for choosing the best email service provider for your needs.

What is an SMTP Relay Service?

SMTP stands for Simple Mail Transfer Protocol, and it’s a secure, reliable delivery protocol used to transmit emails from an email sender to the recipient’s mail server. The process involves two components – the sending SMTP server and the receiving server.


SMTP is an email communication protocol that is used by mail servers to send emails from one account to another via the internet.

On one end, the sending SMTP server will use its SMTP settings (such as authentication credentials) to authenticate itself with the receiving server.

On the other end, the receiving server will use its own set of settings (such as incoming mail protocols) to verify that it can trust messages sent by this particular sender.

Once these two servers have established a connection using their agreed-upon protocols, they will securely exchange messages according to those same standards. In most cases, email message delivery times are usually quite fast due to how quickly an SMTP relay typically works – in some cases, it’s just fractions of a second!

SMTP relays are essential for any organization or individual that sends out large volumes of emails each day as part of their business operations or marketing campaigns. Services like ours not only ensure secure and timely delivery, but they also provide peace of mind knowing that your communications remain private and secure throughout their journey across networks around the world.



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Public vs Authenticated SMTP Relay Services

There are two types of SMTP relay services – public and authenticated.

Public SMTP relay services are typically offered by ISPs and allow anyone to send emails through their network without the need for any authentication. While this may sound convenient, it can also be quite dangerous as it opens up the possibility of abuse (such as spamming).

Authenticated SMTP relay services, on the other hand, require users to provide some form of credentials (usually a username and password) in order to use the service. This authentication step helps to prevent abuse and ensures that only authorized users are able to send emails through the service.

When choosing, it’s important to weigh the pros and cons of each option and decide which one is best for your needs.

For example, if you’re running a large-scale marketing campaign, sending bulk emails, an authenticated SMTP relay service would be a better option as it would provide more control over who is able to send emails through your account; it would also decrease the chances of your message ending up in a spam folder.

On the other hand, if you’re only sending a few emails each day, a public SMTP relay service may be sufficient to assure email deliverability.


Pros and cons of web API and SMTP relay server

Advantages of Using an SMTP Relay Service

Using an SMTP relay server offers several key advantages for organizations and individuals that send out large volumes of emails. These include:

  • Increased Reliability & Delivery Speed

    An SMTP relay service provides a reliable bridge between the sending and receiving servers, ensuring messages are sent quickly without any delays or disruptions in service. This ensures your emails reach their intended destination as soon as possible – often with faster delivery times than traditional email systems.

  • Enhanced Security & Privacy

    As mentioned earlier, an SMTP relay provides increased security by authenticating both the sender’s SMTP server and the recipient’s server before transmitting data back and forth between them. This helps ensure that private information is not intercepted during transit and remains secure until it reaches its intended recipient(s).

  • Reduced Spam Filters & Blocked Messages

    Since most spam filters look for certain indicators when deciding which messages to block or filter, using an SMTP relay can reduce the chance of legitimate messages being blocked and sent to a spam folder due to false positives created by automated filters. With fewer false positives, more of your legitimate emails will make it through to their intended recipients – improving your email deliverability and hence increasing your chances of success with each message you send out!

  • Easier Setup & Management

    Using an external provider simplifies SMTP server setup compared to configuring internal mail SMTP relay servers on-premise (which often require significant IT resources). Additionally, many providers offer user-friendly web interfaces where users can easily manage their accounts and configure settings according to their individual needs – no technical expertise is required!

  • Cost Savings

    By outsourcing your email delivery needs to an external SMTP relay provider, you can save yourself the time and money associated with setting up in-house mail SMTP servers. Not only does this simplify setup and management, but it also eliminates the need for additional IT personnel or resources – meaning you can focus more on growing your business instead of worrying about managing your own SMTP server.

  • Scalability & Flexibility

    Using an external provider also provides more flexibility when it comes to scaling your email delivery needs. With the ability to quickly add or remove SMTP relay services, you can adjust according to current demand and ensure that messages are delivered with little disruption in service – even during peak activity times.

  • Improved Branding & Reputation

    By using an external provider as an SMTP client, you can ensure that your emails are sent from a trusted source, a reliable SMTP relay server – often with a recognizable “from” address. This helps to build trust and credibility for your organization or brand, which in turn can lead to improved customer satisfaction and loyalty.

  • Automated Integration

    Many providers offer integrations with popular third-party services, including EmailLabs, allowing you to delivering and tracking of emails. This helps reduce manual workloads associated with email campaigns and provides detailed insights into message performance – helping you optimize your campaigns for maximum success!

  • Technical Support 

    Having access to technical support from an experienced team is invaluable when it comes to troubleshooting any issues that may arise. Most providers offer 24/7 customer service and knowledgeable experts who can help you quickly resolve any problems – allowing you to get back up and running in no time!

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How to Choose an SMTP Relay Service

When choosing an SMTP relay service, it’s important to consider a few key factors:

  • Cost

    Depending on your needs, you may be able to find free or low-cost services. However, if you need more reliable and secure delivery or higher volumes of emails sent each month, then you will likely have to pay for the service.

  • Reliability & Delivery Speed

    You should look for an SMTP relay provider with reliable and fast delivery times. Additionally, they should have a good track record of email deliverability without any service disruptions.

  • Security & Privacy

    Ensure the provider offers encryption standards such as TLS or SSL, which help protect your data during transit. Also, check to see if they provide other security features, such as two-factor authentication or anti-spam filters.

  • Ease of Setup & Management

    Look for a provider with an easy-to-use web interface where you can configure settings and manage your account quickly and easily – no technical expertise is required!

  • Integrations & Automation

    If you plan on integrating with a third-party service such as EmailLabs for better deliverability of your automated campaigns, then make sure to choose a provider that supports integration. Many providers also offer APIs so you can build custom solutions.

  • Technical Support

    Having access to knowledgeable customer service representatives who are available, 24/7 is invaluable when it comes to troubleshooting problems or resolving issues with your SMTP servers quickly and effectively – look for providers that offer this type of support!

  • Scalability & Flexibility

    Your email delivery needs may change over time – make sure to choose a provider that allows you to add additional SMTP relays or scale down according to demand so there’s never any disruption in service due to sudden changes in volume.

By considering all of these factors, you should be able to find an SMTP relay service that meets your needs and provides reliable, secure delivery for your emails.


In conclusion, an SMTP relay service is an essential part of secure and reliable email delivery. By utilizing a provider’s web-based interface, users can configure their settings to ensure that messages are delivered as expected in a timely manner.

Additionally, the use of TLS encryption helps protect sensitive data from malicious actors or hackers who may be trying to intercept messages in transit.

When selecting an SMTP relay email service provider, it is important to consider factors such as the size and frequency of emails sent, features offered (such as whitelisting/blacklisting), customer support available, and price plans.

Taking all these into account will help you choose the best service for your needs while keeping costs down at the same time. And if you want to know more about configuring SMTP relays, check out our short guide!

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