What is the solution to this SMTP server problem?
Posted: Thu Feb 13, 2025 9:01 am
You may have also come across the term SMTP relay when reading about email marketing. This is a more technical term that refers to the act of routing emails to the correct destination SMTP server on behalf of the sender. It often specifically involves the use of special servers set up by bulk email services (um… like transactional emails sent to recipients from a website or web app, with enhanced deliverability).
In practice, however, the term SMTP relay more often refers to the actual SMTP server that email passes through before reaching its destination, such as a mail processing and distribution center. In this context, you can think of "SMTP relay" as a synonym for SMTP server.
SMTP Server
As we mentioned before, SMTP is a communications protocol used to securely transmit email over the Internet. So what does a server mean?
"Server" is just a fancy word for computer. However, a server functions completely differently than your average personal computer:
A personal computer , such as your laptop or desktop, allows users to store different files locally using an operating system such as Windows or Mac OS, and perform other tasks using applications or client-side web applications.
Servers , on the other hand, are computers used solely to store, process, or transfer data between other servers or personal computers (clients) via requests in order to produce specific functionality for the client software making the request.
In the context of email, the client software is the application you use to access your email (such as Mozilla Thunderbird or Microsoft Outlook) or the webmail inbox provider you use to access your email from a mail delivery agent (such as Gmail or Yahoo). The server is all the other machines that participate in the SMTP process (MDA, MSA, MTA).
These servers run programs that wait for SMTP commands from SMTP clients (senders). Once they receive a command (or request) from an SMTP client, the server establishes a connection with that client and begins routing the electronic message to the correct recipient according to the rules dictated by SMTP (the protocol).
Therefore, any server that receives, processes, transmits, or stores electronic messages transmitted via SMTP can be considered an SMTP server.
However, in the context of email marketing, SMTP servers refer to generic services provided by bulk email platforms. This is because companies like Sendinblue have a large number of dedicated servers that are specifically configured to support high-volume sending for end users (unlike the SMTP servers used to send typical emails from a Gmail account).
SMTP Servers and Deliverability
Now that you have a better understanding of what SMTP means, let's get to what you're really interested in: email deliverability.
The SMTP server you use to send email is associated with a specific IP address. This address is directly related to your deliverability because ISPs use this address to check your sender reputation.
As we mentioned earlier, the SMTP servers set up by classic email providers (Gmail, Yahoo, Outlook, etc.) for sending personal emails are not suitable for handling bulk email sending due to the nature of their services .
The reason for this is that their IPs are not closely monitored. This means that you could be sending emails from the same servers as known spammers. If you try to send bulk emails through a classic email provider like this, you are guaranteed to end up in a spam folder.
If you want the best possible deliverability for your bulk email, you need to use a professional SMTP relay ig database service that is set up explicitly for delivering bulk email.
At Sendinblue, all of our servers are built on a solid and reliable infrastructure that enables us to send millions of emails every day for our customers.
Because we maintain strict control over all IP addresses, users benefit from excellent deliverability rates for both marketing and transactional emails.
If you need more control over your sender reputation, Sendinblue also provides dedicated IP addresses for our large volume senders. This means you don't have to worry about anyone else's sending behavior affecting your deliverability.
In practice, however, the term SMTP relay more often refers to the actual SMTP server that email passes through before reaching its destination, such as a mail processing and distribution center. In this context, you can think of "SMTP relay" as a synonym for SMTP server.
SMTP Server
As we mentioned before, SMTP is a communications protocol used to securely transmit email over the Internet. So what does a server mean?
"Server" is just a fancy word for computer. However, a server functions completely differently than your average personal computer:
A personal computer , such as your laptop or desktop, allows users to store different files locally using an operating system such as Windows or Mac OS, and perform other tasks using applications or client-side web applications.
Servers , on the other hand, are computers used solely to store, process, or transfer data between other servers or personal computers (clients) via requests in order to produce specific functionality for the client software making the request.
In the context of email, the client software is the application you use to access your email (such as Mozilla Thunderbird or Microsoft Outlook) or the webmail inbox provider you use to access your email from a mail delivery agent (such as Gmail or Yahoo). The server is all the other machines that participate in the SMTP process (MDA, MSA, MTA).
These servers run programs that wait for SMTP commands from SMTP clients (senders). Once they receive a command (or request) from an SMTP client, the server establishes a connection with that client and begins routing the electronic message to the correct recipient according to the rules dictated by SMTP (the protocol).
Therefore, any server that receives, processes, transmits, or stores electronic messages transmitted via SMTP can be considered an SMTP server.
However, in the context of email marketing, SMTP servers refer to generic services provided by bulk email platforms. This is because companies like Sendinblue have a large number of dedicated servers that are specifically configured to support high-volume sending for end users (unlike the SMTP servers used to send typical emails from a Gmail account).
SMTP Servers and Deliverability
Now that you have a better understanding of what SMTP means, let's get to what you're really interested in: email deliverability.
The SMTP server you use to send email is associated with a specific IP address. This address is directly related to your deliverability because ISPs use this address to check your sender reputation.
As we mentioned earlier, the SMTP servers set up by classic email providers (Gmail, Yahoo, Outlook, etc.) for sending personal emails are not suitable for handling bulk email sending due to the nature of their services .
The reason for this is that their IPs are not closely monitored. This means that you could be sending emails from the same servers as known spammers. If you try to send bulk emails through a classic email provider like this, you are guaranteed to end up in a spam folder.
If you want the best possible deliverability for your bulk email, you need to use a professional SMTP relay ig database service that is set up explicitly for delivering bulk email.
At Sendinblue, all of our servers are built on a solid and reliable infrastructure that enables us to send millions of emails every day for our customers.
Because we maintain strict control over all IP addresses, users benefit from excellent deliverability rates for both marketing and transactional emails.
If you need more control over your sender reputation, Sendinblue also provides dedicated IP addresses for our large volume senders. This means you don't have to worry about anyone else's sending behavior affecting your deliverability.