How is an email sent? You type it out on your computer, hit send, and it magically reaches your recipient, right? Well, while it may seem like magic, it's mostly thanks to the SMTP server that your email provider set up.

What is an SMTP server?

SMTP stands for Simple Mail Transfer Protocol. SMTP servers are the reason your email reaches your recipient's inbox. SMTP is a protocol—a set of instructions—that dictates the transfer of emails between two servers (sender and recipient), while SMTP servers are the servers that know how to perform this protocol.

Why do we need SMTP servers?

The SMTP server does for emails exactly what the postman does for your physical letters. This server ensures that the email you send from your email client reaches your recipient's inbox intact. The message you hit send on gets converted into a code that can be transported to the SMTP server for processing and relaying.

While the main purpose of modern SMTP servers like ZeptoMail's and Zoho Mail's is to relay emails, the role of modern SMTP servers has extended beyond this:

1. They ensure that your emails are properly authenticated. SPF, DKIM, etc need to be in place while sending emails.

2. Recipient servers can be suspicious of large volumes of emails from a single server. These servers manage the volume to ensure that there is no negative impact on email sending.

3. Modern SMTP servers ensure that the security of their infrastructure is up to date and up to industry standards.

How does SMTP work?

There are multiple steps and processes that take place between hitting the send button (in ZeptoMail's case, once it is triggered from the application) and the recipient receiving the email. Take a look at how this digital postman (SMTP server) works in sending an email from ZeptoMail to a recipient using Zoho Mail:

1. As soon as the email is triggered, your email client establishes a connection with the ZeptoMail SMTP server.
2. The email client conveys the details of the message, sender, and recipient with the ZeptoMail SMTP server.
3. Once it has the information about the recipient server, ZeptoMail's SMTP server runs a check to verify that the sender is an active email account to prevent spam.
4. The ZeptoMail SMTP server then processes the information sent by the email client.
5. It first identifies the recipient domain and the SMTP provider hosting the domain. The SMTP server also gets the recipient provider's unique IP address.
6. After the verification is successful, ZeptoMail's SMTP server hands over the message to the recipient SMTP server—in our case, the Zoho Mail SMTP server.
7. Once the email is delivered, recipient servers perform a list of actions like checking the sending server's reputation, MIME format, SPF and DKIM verifications, etc. After their checks are performed, the server then delivers the email to the inbox or spam folder, quarantines the email, or rejects the email.

What is SMTP security and why is it important?

Considering that your SMTP server literally handles every single email you send out, you would want to reinforce the security of this crucial connection. So why do we need SMTP security?

Unauthorized access

Important information is transmitted via email. Without good SMTP security in place, unauthorized people can gain access to your emails. This data can then be leaked or used for their advantage.

Spam and phishing

If an unauthorized person gets access to your SMTP credentials, they can send out spam emails to your contacts. In some cases, they can also impersonate you and send malicious emails to your contacts and gain confidential information.

Deliverability issues

Once these fraudsters use your SMTP server for spamming and phishing, email providers will view your emails as untrustworthy. This will end up causing deliverability issues for your legitimate emails.

Malware and email attacks

Attackers can use your SMTP credentials to spread malicious software to recipients of your emails and also within your own systems. They can also use SMTP access to perform email attacks like DDOS to harm other servers.

If you're wondering if there is a simple way to send emails securely using SMTP, there definitely is.

ZeptoMail is a transactional email-sending service that lets you send transactional emails from your application/sites using SMTP. You can use the SMTP configuration to send emails in a quick few steps.

You also don't need to worry about securing the SMTP server—we've got it covered.

How we secure your SMTP connection

ZeptoMail takes multiple measures to protect your email sending over our SMTP connection.

Secure SMTP

ZeptoMail adds a layer of security by using TLS connections. SSL/TLS connections encrypt the email message when being sent from the email client to the SMTP server. So even if the server is breached, attackers will only be able to see codes that cannot be deciphered. ZeptoMail supports TLS v1.2 to eliminate the limitations of previous versions.

SMTP account authentication

SMTP email sending in ZeptoMail is done using unique passwords. When your application connects to our SMTP, your identity is verified using the password. Each Mail Agent comes with unique SMTP credentials that allow you to isolate the reputation of different email categories that can be based on type, application, purpose, environment, and more.

Domain verification

The first and most crucial step in ZeptoMail onboarding is domain verification. Every domain added to our platform is authenticated using SPF, DKIM, and CNAME. This helps prove your identity to our SMTP server and also protects you from spammers and spoofing. You can also publish DMARC policy to advise the recipient server on how to handle emails that originate from your server.

IP restrictions

ZeptoMail lets you manage email sending from different IPs using IP restrictions. You can add IP addresses/ranges from which you allow email sending. While your account can be accessed from any IP, email sending can only occur from the provided IP addresses.

These are just some of the security measures ZeptoMail has in place. We also have email APIs that allow for deeper integration of your application/site with ZeptoMail.

And that's all we have for today—I'll be back to tell you more about these features in our upcoming blogs. Trust me that we're hard at work coming up with more ways to make your ZeptoMail experience even better! In the meantime, give our latest updates a try and share your feedback with us on social media, through email, or in the comments below!

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