Why SMTP is not used?

Why SMTP is not used?

Simple Mail Transfer Protocol (SMTP) is a standard protocol for sending emails across the internet. It was created in 1982 and allows applications to route and deliver emails between servers and clients.

Why SMTP is not used?

While SMTP is still commonly used today, especially by internet service providers (ISPs) and small businesses with basic email needs, there are some key reasons why many modern organizations are moving away from using the SMTP protocol directly for sending emails:

Security and Encryption

One of the main drawbacks of SMTP is that by default it has very limited security and encryption capabilities:

  • SMTP connections and email content are not encrypted. This leaves emails vulnerable to interception and hacking.
  • SMTP lacks strong authentication mechanisms. Mail servers validate using just a username and password, which is weak compared to modern standards.
  • Spam filters have improved, but SMTP still enables high volumes of spam, phishing attacks, and email fraud.

As cybersecurity threats have evolved, these SMTP security gaps have become increasingly problematic for organizations handling sensitive communications and data.

Reliability and Deliverability Issues

SMTP servers can be unreliable for consistent and metrics-driven email sending:

  • There is no guarantee an email was successfully delivered and opened by the recipient when using SMTP alone.
  • SMTP has difficulties with scalability. As email volume increases, deliverability issues also tend to increase.
  • Simple things like changing an IP address can negatively impact email sender reputation and deliverability over time.

Bulk and transactional email senders require reliable metrics and deliverability. SMTP cannot provide insight on opens, clicks, unsubscribes, spam reports, etc.

Difficult to Scale and Maintain

Maintaining your own SMTP servers and infrastructure for large volume, business-critical email sending also comes with downsides:

  • Managing backups, security updates, storage capacity, redundancy, scaling, and continuity for SMTP servers incurs significant IT overhead costs.
  • Email sender reputation with major ISPs needs to be maintained to ensure good inbox placement rates. This requires experience with email deliverability best practices.
  • Building custom software and tooling for metrics, analytics, compliance, storage of sent emails, etc. all has to be handled internally.

Alternatives to SMTP for Sending Email

Given these expanding challenges and limitations, SMTP alone is no longer a viable scalable email sending solution for many modern organizations.

Common alternatives used instead of SMTP today include:

  • API Email Services – Services like SendGrid, Mailgun, Mailchimp, etc. that offer email APIs and webhooks to easily integrate transactional and marketing email. These build reliability, security, and analytics on top of SMTP’s core protocol while abstracting infrastructure away from developers.
  • MTA Servers – Mail transfer agents like Microsoft Exchange, PostFix, and Sendmail help improve security, deliverability, and reliability compared to raw SMTP while still relying largely on the SMTP protocol behind the scenes.
  • In-App Messaging – Where allowed by customers, embedded messaging within web and mobile apps provides an alternative to SMTP-based emails.

So in summary – the core SMTP protocol still underpins much of email sending online today, but is no longer used directly by many sophisticated, security-conscious organizations due to inherent protocol limitations leading to expansive modern alternatives.

Key Takeaways

  • SMTP lacks strong encryption and security capabilities leading organizations to seek alternatives to protect sensitive communications.
  • Unreliable deliverability and lack of delivery metrics make tracking and optimization difficult with SMTP email sending.
  • Maintaining SMTP infrastructure and reputation at scale requires expertise many organizations cannot build internally.
  • Popular SMTP alternatives include managed API email services, MTA servers that improve upon SMTP capabilities, and in-app messaging where email is not strictly required.


SMTP revolutionized email in the early days of the internet by defining a standard protocol to reliably route messages between servers. However, increasing security threats combined with limited analytics capability and infrastructure challenges have made SMTP less practical for many modern organizations.

As email’s role continues to rapidly evolve with rising volumes and customer expectations around deliverability, security, and engagement tracking, purpose-built email sending platforms and technologies have proliferated. So while SMTP persists behind the scenes moving emails between servers, directly using SMTP is no longer the best practice for most transactional and marketing email sending needs today outside of basic use cases. Alternatives like SendGrid combined with communication trends like in-app messaging provide more compelling solutions.

Frequently Asked Questions

What are the disadvantages of SMTP?
The main disadvantages of SMTP are no encryption leading to security issues, lack of reliable email delivery and engagement tracking metrics, scaling difficulty for high email volumes, and infrastructure/reputation maintenance overhead.

Why is SMTP not secure?
By default SMTP does not encrypt connections or email content, enabling interception and hacking vulnerabilities. It also lacks strong authentication mechanisms, relying on weak username/password validation.

Does SMTP provide delivery confirmation?
No, SMTP does not reliably confirm delivery or engagement tracking – it simply forwards an email to the next mail server. Without additional functionality there is no guarantee the recipient receives or opens the email.

Can SMTP scale to handle large email volumes?
SMTP can struggle to scale reliably for sending high email volumes typically associated with business, marketing, or transactional email sending needs. Its decentralization creates potential for deliverability issues.

Does SMTP work with Office 365?
Yes, Office 365’s Exchange Online mail servers use SMTP protocol & ports behind the scenes while adding security, reliability, analytics, and manageability. But the servers handle SMTP processes – direct SMTP connections are not an option.

Is SMTP still used today?
SMTP is still widely used today to route emails between mail servers over the internet. But most organizations use API email services or servers that improve upon SMTP directly for sending emails, while leveraging SMTP behind the scenes.

Is SendGrid SMTP?
SendGrid is not an SMTP server. SendGrid manages infrastructure reliability and scalability behind its email API, while leveraging SMTP to efficiently route emails between its servers and destination email servers where recipients have accounts.

Is Gmail SMTP?
Gmail utilizes SMTP for sending emails behind its friendly web interface and mobile apps. However, Gmail does not allow users to directly connect with SMTP due to security and deliverability considerations.

What are the alternatives to SMTP?
Top alternatives to direct SMTP for sending email include managed API email services like SendGrid & Mailgun, MTAs like Microsoft Exchange and Postfix, and in-app messaging where appropriate. These improve security, deliverability, and analytics capability compared to raw SMTP.

What is a SMTP server and how does it work?
A SMTP server implements the SMTP protocol to route and transport outgoing emails to destination servers using DNS MX records. Users connect SMTP clients to the server which then handles authentication, acceptance, routing, and delivery processes before handing emails off to the next server.

Why SendGrid over SMTP?
SendGrid provides improved deliverability, security, reliability, and analytics over standard SMTP through dedicated IP addresses, email authentication, open & click tracking, advanced SMTP API functionality, and automated scaling to send high volumes without impacting deliverability.

Can I use Gmail or Outlook SMTP?
You cannot directly connect to consumer Gmail or Outlook SMTP servers. They are intended for user account access, not bulk sending. Instead you would use a dedicated email API service or server solution tailored for transactional and marketing email at scale.

Is SMTP faster than API email?
Typically not – API email platforms like SendGrid are highly optimized for fast sending through purpose-built infrastructure. SMTP requires managing your own server scaling and deliverability considerations at lower level. An email API offloads that complexity for speed.

Does SMTP thread emails?
No, standard SMTP does not support email threading – that’s handled at the mailbox provider level (Gmail, Outlook, etc). SendGrid does offer a Conversation ID header to support threading transactional emails within mailboxes that implement threading capability.

Can SMTP relay be used to send emails?
Yes, configuring an SMTP relay entails hardening & restricting a public facing SMTP server to only allow specified hosts to send outbound email through it, adding a layer of security. This leverages the native protocol while limiting exposure.

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