BSG utilizes HTTP cookies (and similar or complementary technologies) to 1) make this website safe, functional, and accessible (through the use of mandatory cookies) and 2) understand how you use our website (through the use of optional cookies) in order to improve your experience and to provide you with personalized content.

The information in the cookie text files may be related to your personal preferences or your device and is intended to make the site operate according to your expectations. The information contained in cookies does not usually identify your identity directly but is helpful in providing you with a more personalized user experience.

In accordance with the requirements of the General Data Protection Regulation (GDPR) privacy and security law that governs how the personal data of individuals in the EU may be processed and transferred, we provide you the possibility to prohibit the use of certain types of cookies when you use our website.

Read our Cookie Notice and the Privacy Policy for detailed information on how BGS collects and uses cookies. Please note that prohibiting the use of certain types of cookies may affect your interaction with the website and limit the accessibility of services we offer you. Choose the appropriate category below to learn more and to disable cookies.

Accept All cookies*
*Recommended for comfortable use of the site
Accept only necessary cookies
Accept only selected cookies
Necessary cookies
Social media
Analytics
Marketing

Simple Mail Transfer Protocol (SMTP)

What is Simple Mail Transfer Protocol (SMTP)?

Simple Mail Transfer Protocol (SMTP) is a protocol used for sending and receiving emails. It is the standard protocol used for email transmission over the internet and is responsible for routing emails and ensuring they reach their destination. SMTP is a text-based protocol and uses commands such as “HELO,” “MAIL,” and “RCPT” to communicate with mail servers.

SMTP is a client-server protocol, meaning that it requires two computers to communicate; a client, which initiates the communication, and a server, which responds to the client’s requests. When an email is sent, the client sends a command to the receiving mail server, which then checks its database to make sure the address is valid and then forwards the message to the recipient’s email address. If the recipient’s address is valid, the server responds with an “OK” message, and the email is delivered.

For additional security, SMTP uses various authentication methods, such as TLS and SSL, to ensure that only authorized users can send and receive emails. Additionally, SMTP also supports encryption, so that emails can be securely transmitted over the internet.

SMTP is an essential protocol for the functioning of the internet and is used by most email servers, webmail services, and email clients.

How does it work?

When you send an email, the client (your computer) establishes a connection with the server (the recipient’s mail server) using the SMTP protocol. The client then sends a “HELO” command, which the server responds to with its own “HELO” message. The client then sends a “MAIL FROM” command, which specifies the sender’s email address, followed by an “RCPT TO” command that specifies the recipient’s email address.

Once the server has verified the addresses, it sends a response of “OK” and the email can be sent. The client then sends the message in plain-text format, and the server sends a response of “OK” to indicate that the message has been received. The server then attempts to deliver the message to the recipient’s mailbox. If the message is successfully delivered, the server sends a response code of “250” to indicate success.

Interested in a special offer?

Ready to reach further?
Let’s talk

I agree to BSG privacy policy
Submit

Useful Materials

What Is Number Verifier — And Why It’s More Than Just an “HLR Lookup”

30% of SMS fail — not because of content, but numbers. Verify before you send.

10 Awesome Back-to-School Marketing Ideas 2025

The start of the school year: when parents trade in their summer margaritas for the

What Is CPaaS? Communications Platform as a Service

Talking to customers these days is more than just emails or phone calls. Businesses need