Choosing between ESP vs SMTP Relay Services

When selecting a bulk email solution, one of the first broad choices is whether to use an SMTP relay [or transactional mailing system] or a full ESP service. This article outlines the differences between the solutions, and outlines how to go about choosing the correct option for your business.

The basic difference

Email Service Provider vs Simple mail Transfer ProtocolAn SMTP (Simple Mail Transfer Protocol) service is simply a bulk email delivery service (without all of the features that you would expect from marketing email service provider). Think about services such as Amazon SES... this is an SMTP service.

The basic principle of these systems is that you need the ability to create the content of your emails yourself, and then simply connect to these services for the ability to deliver email in bulk. Alternatively, you have the option to use an ESP (Email Service Provider), which is a service dedicated to creating mailer templates, providing tools to manage your subscriber database, segment your subscribers and report in detail on your results.


Service Bulk email delivery Campaign/email design In-platform database management Tracking Campaign management tools
SMTP X limited

  It’s clear based on the table above that ESP’s offer a wider service offering, however SMTP has a key place in the mailing environment due to both price and application. In this article we’ll explore some of the benefits and challenges to using each of these servers for your business.

SMTP – the ins and outs

SMTP is the best solution for a company that has the tools and expertise to manage both their database, and to create their own email content. Consider a large e-commerce platform that has a dedicated email team with database admins, coders and email marketing professionals. With a team such as this it is in fact beneficial to run your own email program in house and to simply use a cheap SMTP to act as an MTA [mail transfer agent]. This works out far cheaper, and also allows you to keep all of your data in house. Another appropriate example for a smaller user might be if you have a unique business model and only need to send very simple content, such as login confirmations or password resets, and you have the technical ability to design your own emails and connect to an SMTP relay to deliver your mails.

In cases like these you may well want to use a simple SMTP service…its cheap and gets the job done according to your needs.

In summary, the key advantages of SMTP are that:

  1. You can keep your data on site, rather than permanently storing it with an ESP.
  2. They are often more than 75% cheaper than Email Service Providers.
  3. If you have the technical know-how, then they do offer great delivery when properly managed and can do a fine job of delivering your mail.

However, a couple of downsides that often outweigh these advantages:

  • A lack of list management capabilities – SMTP services don’t allow you to effectively segment and manage mailing lists. Not only will this create an administrative mess, it could also lead to a number of mails going to dead email addresses or to recipients receiving mails that aren’t relevant to them or that they do not want to opt in for if you do not implement the monitoring on your own side. This is expensive and technically challenging.
  • No prebuilt mailer templates, or template design services – every mail you send will need to be designed and written from scratch, due to the fact that you won’t have access to custom, pre-built templates. This can waste valuable resources if you are sending emails to your database regularly. If you’re using an SMTP server for newsletters, you’ll quickly become aware of how tedious it can be to create them from scratch.
  • Tracking shortcomings– perhaps one of the most integral aspects of an email marketing campaign is the collection of data, which is not available through the use of an SMTP server to nearly the same degree. Insights from data help you to determine the success of the campaign and pinpoint gaps where communications can be improved upon. Access to data that you can analyze and track will help you deliver high-quality information to clients and business owners alike.
  • Infrastructure limitations – Certain SMTP servers are often overloaded and take eons to deliver messaging and notifications. This can cause issues when promoting time-sensitive specials for example.

Email Service Providers:

It’s no secret that consultants will recommend the ESP option for businesses of almost any size. While SMTP has its place, most businesses lack the skill to properly use them Here’s why:

ESPs cover all the bases:

  • Usability – with an ESP, you can create mailer templates that are quick and easy to amend for each new campaign. You also get access to an interface that has been designed for non-technical users to manage the technical discipline of bulk mailing. This saves on time and resources, ensuring a quicker and more efficient mailing system.
  • Clean, permission-based mailing lists – in keeping with various global laws regulating online communications, ESP’s will ensure that unsubscribe requests and bounces are correctly handled. This can save you serious legal implications.
  • Support –an ESP is able to provide you with tech and system support when crafting your campaigns, this is an absolute necessity for most senders. If any issues arise, you can contact your ESP directly for quick and efficient resolution.
  • Spam scoring tools – ESP’s allow you to run a basic Bayesian spam scoring test on your mail before sending it out. They can measure what is likely to go through and what isn’t - using spam-scoring software.

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