Mail and SMTP (Simple Mail Transfer Protocol) are both methods for sending electronic messages over the internet, but they operate in different ways.
Mail typically refers to email applications like Outlook or webmail services that end users interact with to send and receive messages. When a user composes an email in a mail application, the software directly connects to a mail server to submit it for delivery.
Key aspects of mail:
- Mail applications allow users to compose, send, organize, and read email messages through an interface. Webmail provides this via a web browser while other clients run as desktop or mobile apps.
- When sending messages, the mail software directly interacts with a mail server, which distributes messages to recipients based on address information.
- On the receiving end, mail applications retrieve messages from a mail server connected to the user’s account whenever they conduct an inbox refresh or manual send/receive action.
- Email providers maintain their own dedicated mail servers like Microsoft Exchange to process their customers’ mail traffic.
How SMTP works
SMTP stands for Simple Mail Transfer Protocol and is the underlying system that governs email transmission between mail servers over the internet. It sets the rules for how messages should be routed and handled as they travel from one server to another until reaching the recipient’s mail provider.
Core aspects of SMTP:
- It is mainly used for sending outbound mail. When users submit a message via a mail application, their provider’s mail server connects to the receiving server via SMTP to handle the transmission.
- All mail servers on the internet communicate with each other using the SMTP protocol to initiate email sending sessions and agree on formatting standards.
- As messages pass from their origin to destination, each mail server along the route uses SMTP commands to send and relay the email towards its final address through a series of handoffs.
- Common SMTP connection ports including 587 and 25 handle high volumes of standardized traffic between mail servers. Security extensions like STARTTLS encrypt connections.
- Because it focuses exclusively on server-to-server transmission rather than end user functionality, SMTP itself provides no means for users to directly read or compose emails.
|Enables users to directly access, read, compose, and manage email messages.
|Facilitates server-to-server communication to route messages between providers over the internet.
|Provides user-facing email applications and services.
|Handles background email transmission between servers.
|Mail apps log into mail servers directly for send/receive functions.
|Mail servers communicate via SMTP, which user email programs do not directly interact with or access.
|Outbound: Mail apps submit messages to servers for delivery. <br> Inbound: Apps poll for newly delivered mail.
|Servers establish SMTP connections to send and relay batches of queued email data to recipients’ servers.
|Optional end-to-end email encryption services available.
|Heavily relies on SMTP security extensions like TLS for encrypted transmission between servers.
In summary, mail creates an email access experience around SMTP’s server distribution pipeline that delivers messages to their intended destinations.
- Mail refers broadly to end user email applications while SMTP is a protocol used for message routing between mail servers.
- When users submit mail via a client, their mail server uses SMTP procedures to transfer messages across various servers that ultimately deposit the email into the recipients’ accounts.
- SMTP powers background routing while mail apps focus on user-side services like composing messages within an email provider interface and accessing received messages.
- Together they create a full-cycle system allowing users to exchange electronic messages seamlessly with recipients on other mail providers over the internet.
Although the general concept of “email” blends together mail and SMTP functions, they operate complimentary layers enabling distinct services. SMTP manages the networking layer, setting common language and transport rules that allow isolated mail servers to relay billions of messages. Meanwhile, mail applications utilize this infrastructure to give users intuitive tools to leverage email communication in their daily lives. Their symbiosis delivers one of today’s most widely used internet communication mechanisms.
Frequently Asked Questions
Q: Can regular users directly interact with SMTP to send emails?
A: No, SMTP is designed as a background protocol that only mail servers interact with. Normal users access user-facing mail applications to send messages.
Q: Does SMTP handle tasks like organizing mail into folders or spam detection?
A: No, SMTP solely focuses on establishing connections for message transport between mail servers. Mail applications provide value-added user services like spam filtering.
Q: Do webmail services rely on SMTP?
A: Yes, all mail sent online through webmail apps ultimately uses SMTP protocols behind the scenes when messages transit from the user’s email provider server to the receiving mail server.
Q: Is SMTP used exclusively for email?
A: Primarily yes, though SMTP principles help handle some other communication functions like sending notifications or alerts electronically. But its core purpose is enabling email transport.
Q: Can messages be sent between mail servers if they use different SMTP implementations?
A: Strict SMTP standards allow diverse vendor server hardware and software to interoperate. So mail can route between, say, Exchange and Sendmail servers due to common protocols.
Q: Does SMTP involve mailbox creation and management?
A: No, SMTP focuses purely on message transport, while user account creation and disk space allocation for storing messages falls within mail administrators’ purview.
Q: What are the most common SMTP ports?
A: Port 25 handles SMTP traffic by default. And for connections encrypted by TLS/SSL, ports 587 and 465 are also popular options.
Q: Does Microsoft Outlook interact directly with SMTP?
A: Outlook leverages Microsoft Exchange’s built-in SMTP services for routing outbound messages to other mail hosts using defined routing paths and connectors.
Q: Can SMTP transmit email attachments?
A: Yes, MIME encoding extensions enable SMTP standards to support attachments while also handling special characters and non-ASCII text.
Q: Are there other well-known protocols that handle email besides SMTP?
A: IMAP and POP3 handle user access to stored email, focusing more on retrieval than transport.
Q: What are the key security concerns surrounding SMTP?
A: Spoofing attacks, interception of unencrypted mail, falsified sender addresses, and use to distribute malware payloads rank among top issues.
Q: Does SMTP provide built-in identity verification?
A: No, add-on protocols like SPF, DKIM and DMARC help confirm sender identities to combat spoofing threats at domain levels.
Q: How has SMTP evolved over time?
A: Updates like 8BITMIME, SMTPUTF8, STARTTLS encryption, DANE TLSA records, SMTP Auth, and SMTP Submit refine the protocol in areas like security, encoding, and authentication.
Q: What is the difference between TCP and SMTP connections?
A: TCP enables device networking, while SMTP outlines specific syntax standards for servers to exchange mail data reliably over TCP’s foundational connection pipeline.
Q: Can typical home internet subscribers run their own SMTP servers?
A: Most residential ISPs block outbound TCP port 25 to reduce spam abuse. But subscribers can often still legally operate SMTP servers on non-standard ports.
Q: What are some examples of popular SMTP server applications?
A: Sendmail, Postfix, Exim, and Microsoft Exchange Server comprise some major examples that power email delivery for many large providers.
Q: How does clustered or multi-node SMTP configuration work?
A: Grouping sharded servers behind load balancers allows high-volume SMTP applications to scale mail intake and delivery while sharing workload.